In-sewer treatment of wastewater and sludges

ABSTRACT

A method and apparatus for in-sewer wastewater treatment comprising steps of largely spontaneously growing acidogenic bacteria in sewer lines and providing methanogenic bacteria in these lines. Methanogenic bacteria can be grown using wastewater, solid, or other waste, or other organic feedstock as a substrate. Methanogenic bacteria can be cultivated at a wastewater treatment plant or at other locations in special reactors, or provided from anaerobic wastewater pretreatment plants. Digestion gases can be either vented out or collected and used.

This application is a continuation-in-part of Ser. No. 08/532,606, filedOct. 12, 1995, now U.S. Pat. No. 5,616,241, issued Apr. 1, 1997, whichis a continuation-in-part of Ser. No. 08/181,387 filed Jan. 13, 1994,now U.S. Pat. No. 5,514,278, issued May 7, 1996, which is acontinuation-in-part of Ser. No. 08/102,618, filed Aug. 5, 1993, nowU.S. Pat. No. 5,514,277, issued May 7, 1996, which is acontinuation-in-part of Ser. No. 08/046,788, filed Apr. 12, 1993, nowabandoned.

BACKGROUND OF INVENTION

1. Field of Invention

This Invention relates to biological treament of Wastewater within sewerpipes, particularly by the use of the acidogenic bacteria growing in thesewer lines and by providing in these lines the conditioned sludgeenriched in in other bacteria types.

2. Description of the Prior Art

Many biological technologies have been first applied to the wastewatertreatment, and later used in other applications, sometimes related toenvironmental technologies, wastewater management and treatment methodsand apparatuses are described in literature, for example, in thefollowing sources:

Water and Wastewater Engineering, Vols 1 and 2 by Gordon Maskew Fair,John Charles Geyer and Daniel Alexander Okun, John Wiley & Sons, 1958;

Biological Waste Treatment, by Wesley W. Eckenfelder and Donald J.O'Connor, Pergamon Press, 1961;

Water Preparation for Industrial and Public Water Supplies, by A. A.Kastalsky and D. M. Mints, Publishing House Higher Education, Moscow,1962 (Russian);

Treatment of Natural Waters, by V. A. Klyachko and I. E. Apeltsin,Publishing House Stroyizdat, Moscow, 1971 (Russian);

Physical Chemical Processes, by Walter J. Weber, Wiley-Interscience, NewYork, 1971;

"Anaerobic Waste Treatment Fundamentals", by Perry L. McCarty, PublicWorks, pp.107-112, September 1974, pp. 123-126, October 1974, pp 91-94,November 1974, pp. 95-99, December 1974;

Biochemical Treatment of Wastewater from Organic ChemicalsManufacturing, by F. V. Porutsky, Moskow, Publishing House Khimia, 1975(Russian);

Chemistry for Environmental Engineering, by Clair N. Sawyer and Perry L.McCarty, McGraw-Hill, 1978;

Metcalf & Eddy's Wastewater Engineering, Vols 1 and 2, Edited by GeorgeTchobanoglous, McGraw-Hill, 1979;

Biological Process Design by Larry D. Benefield and Clifford W. Randall,Prentice Hall, 1980;

Water Chemistry by Vernon L. Snoeyink and David Jenkins, John Wiley &Sons, 1980;

Biological Wastewater Treatment by C. P. Leslie Grady and Henry C. Lim,Marcel Dekker, Inc., 1980;

Low-Maintenance. Mechanically Simple Wastewater Treatment Systems byLinvil G. Rich, McGraw-Hill Book Company, 1980;

Biochemical Processes in Wastewater Treatment by S. V. Yakovlev and T.A. Karyukhina, Stroyizdat, Moscow, 1980 (Russian);

Handbook on Design of Wastewater Treatment Systems, Edited by V. N.Samokhin and Boris M. Khudenko, Allerton Press, New York, 1986;

Treatment of Wastewater Sludaes by I. S. Turovskyi, Stroyizdat, Moscow,1988 (Russian);

Utilization of Wastewater Sludges by A. Z. Evilevich and M. A.Evilevich, Stroyizdat, Sankt Peterburg, 1988;

Industrial Water and Wastewater Systems by S. V. Yakovlev, Ya. A.Karelin, Yu. M. Laskov, Yu. V. Vorononv, Publishing House Stroyizdat,Moscow, 1990 (Russian);

Design of Anaerobic Processes for the Treatment of Industrial andMunicipal Wastes Edited by Joseph F. Malina and Frederick G. Pohland,Technomic Publishing Co., 1992.

Various fundamental and practical aspects of the relevant water andwastewater management and treatment processes are described in the abovelisted sources. These data are also applicable to other processes, forexample, conversion of solid and liquid waste and other materials intobiogas and biological fertilizers and soil augmentation substances.

The generally accepted wastewater management method comprises steps ofcollecting wastewater in a system of pipes and channels, transporting itby these pipes and channels to a treatment works, treating it at thesaid treatment works, discharging the treated effluent into naturalbodies of water or on land, or reusing it for water supplies.

The existing wastewater management systems have the followingdisadvantages:

1. Under anaerobic conditions in the collection pipelines, wastewater inthe bulk flow becomes acidified. Volatile and nonvolatile fatty acidsare formed, and sulfates are substantially reduced to sulfides, whilefatty acids are partially converted to methane. At the gas-waterinterface in the pipes, sulfuric acid is formed. Therefore, theprocesses in pipelines can only cause the formation of odorous,poisonous, ignitable and explosive gases, and corrosion of pipes.Similar problems occur at the front end of wastewater treatment plant.Sometimes odor problems may become severe.

Several methods for controlling anaerobic processes in the sewernetworks have been used: providing oxidative environment, for example byventilation of the pipes with air, or by addition of other oxidants; bydepressing the growth of sulfate reducing organisms with chemicalseffecting specific biochemical steps; or, by raising wastewater pH. Allsuch measures add to the cost of wastewater management and are notfocused on wastewater treatment.

2. The wastewater treatment systems are complex, energy demanding, andexpensive to build and operate. Improvements to the wastewater treatmentfacilities is an ongoing process; however, these improvements areseparate from the improvements in the collection and separationnetworks.

Several modifications of wastewater treatment processes have beendeveloped: 1. aerobic (activated sludge process, lagoon systems, andbiofiltration), 2. anaerobic (various attached and suspended growthprocesses), and 3. coupled anaerobic-aerobic systems. Modern biologicaltreatment systems are used for removal of organics and suspended solids,and for control of nutrients. However, these processes do not achievethorough removal of organics, especially when measured in COD or TOCunits, and removals of nitrogen and phosphorous are marginal. The priorart technologies do not provide controls over the balances of organics,nutrients, biomass, and other constituents of wastewater. In suspendedgrowth aerobic systems, sludge recycle from the final sludge separatorto the head of the treatment process is provided. These systems oftenincorporate several functional zones, usually called anaerobic(nonaerated, preferably, with low nitrate and nitrite in the feed),anoxic (nonaerated, nitrite and nitrate present in the feed water) andaerobic (aerated, dissolved oxygen present in the water, nitrificationoccurs). Mixed liquor is recycled from downstream zones to upstreamzones and the separated activated sludge is recycled from the finalclarifier to the head of the process. A so-called single sludge iscultivated in all these zones. This is predominantly aerobic sludge. Itincludes very few strictly anaerobic organisms. Facultative anaerobicorganisms develop in the nonaerated zone; therefore, the nonaerated zonein these systems should be more properly called the facultative zone.This term will be used in this application. The sludge recycle from thefinal clarifier is intended mainly for controlling the average sludgeage, or average for the system food to microorganism (F/M) ratio. Theupstream facultative zone serves to control the filamentous growth(selector zone) and to release phosphorous for, as believed, itsimproved uptake in the aerobic zone. The facultatively anaerobicorganisms are circulated with the sludge throughout the system. Anoxiczones are used for denitrification: the biological reduction of nitritesand nitrates formed in the aerobic zone and directed to the anoxic zonewith the mixed liquor. These systems are used for treatment of municipaland low to moderately strong industrial wastewater. Examples of thesesystems are described in U.S. Pat. No. 3,964,998 and U.S. Pat. No.4,867,883. The disadvantages of such systems include the following:

single predominantly aerobic sludge is formed in the system, such sludgehaving a poor diversity of species and a narrow range ofoxidation-reduction and biodegradation ability;

process can be used only for dilute to moderately strong wastewater;

sludge concentration along the process train and along major processzones is almost uniform;

FIM ratio in various process zones varies drastically;

in the downstream sections, the wastewater concentrations are low, whilethe sludge concentration is about the same as upstream; accordingly,sludge dies off from lack of food, releasing nitrogen, phosphorus, andorganics back into the water;

sludge generation by mass and volume is high, so the sludge disposalcosts are high;

sludge age is high and so is the corresponding degree of sludgestabilization;

at high sludge stabilization, the content of organics anaerobicallyconvertible to methane is low and Eso is the sludge mass and volumereduction in this conversion;

degradation of soluble organics is poor due to limitedoxidation-reduction potential (OPR) range, especially xenobiotic,recalcitrant or poorly degradable organics (halogenated, and others);

usually, the SS content in the influent to the ASP process is limited byabout 100 mg/l, otherwise removal of suspended solids is poor;

process stability in response to dynamic overloading and toxic shocks islow;

volatile organics may be emitted to the air in facultative, anoxic andaeration sections.

Anaerobic treatment of wastewater and wastewater sludges is well knownin the art. In the past this technology was used mainly for sludgedigestion and for simplified treatment of small wastewater streams inseptic tanks. Recently, the anaerobic method has been applied to treatlarger flows of a more concentrated industrial wastewater, primarily inthe food and beverage industries. These more recent applications haverevealed general advantages and disadvantages of anaerobic treatmentmethods. Additionally, fundamental research has been conducted ontreatment of more complex wastewater, including industrial wastewatersamples and imitations thereof with poorly degradable and toxicorganics. This research demonstrated additional capabilities, advantagesand problems associated with anaerobic processes. The present status ofanaerobic treatment technologies is very thoroughly described in arecent book, Design of Anaerobic Processes for the Treatment ofIndustrial and Municipal Wastes, edited by J. F. Malina and F. G.Pohland, Technomic Publishing Inc., 1992. Additionally, in 1992-1993 theapplicant conducted a study of anaerobic treatment of a complexwastewater, which is used in this application to demonstrate advantagesof the new and improved method.

Two major anaerobic treatment methods were developed in the past: (1)attached growth processes; and, (2) suspended growth processes. Somemodifications are classified as hybrids of these methods. Advantages anddisadvantages of prior methods are given in the above mentioned book.The major advantages of anaerobic systems are the low energyrequirements, with potentially a net generation of energy, and arelative simplicity of treatment units and operations. Disadvantages ofprior anaerobic treatment systems are summarized as follows:

1. Only wastewater with simple soluble substrate (easily degradablenontoxic constituents) can be adequately treated anaerobically.

2. Suspended solids in the wastewater influernt are not satisfactorilydegraded unless retention time in the reactor is very long (usually 3 to15 days or longer). Long retention time requires excessive reactorvolumes as in low rate processes, which are difficult to mix well, andtherefore, breakthroughs of pockets of poorly mixed and poorly treatedwaste occur. This reduces average efficiency of treatment.

3. Slowly and poorly degradable, or toxic, soluble constituents of thewastewater influent are not degraded unless retention time in thereactor is very long, or a bed of granular activated carbon (GAC) isprovided. In the latter case, a portion of the GAC bed must beperiodically replaced due to the accumulation of nondegraded adsorbedmaterial.

4. Liquid in anaerobic reactors often turns acidic due to theaccumulation of fatty acids. This can be caused by an overloading withorganics, or by a toxic effect of specific constituents in the feed orby poor mixing in low rate processes. Accumulation of fatty acids andthe respective drop in pH cause depletion in the methanogenicpopulation. Further accumulation of fatty acids may cause suppression inthe growth of acidogens. Inadequate growth of either group of organismsresults in a process upset. There are no means for controllablecultivation, maintenance, accumulation and use of major groups oforganisms in the prior art anaerobic systems. Since methanogenicorganisms have very slow growth rate, the anaerobic process recoverytakes a long time. This problem becomes especially difficult duringstart-up operations because acidity control requires large quantities ofalkalies, and the start-up process may last many months, and sometimes ayear or longer. Process controls, except pH correction with reagents,are not provided

5. Toxic discharges (for example, slugs of acidic or alkalinicwastewater, or wastewater having elevated concentrations of toxicconstituents) can poison the entire sludge population in the reactor,thus requiring a long restarting time.

6. Either thermophilic (about 55° C.) or mesophilic (about 33° C.) areused. At temperatures lower than mesophilic, the process rate becomesvery slow.

7. Sludge concentration in the suspended growth processes is low,usually from 10 to 60 g/l. Accordingly, substantial effort is requiredto dewater sludges by using centrifuges, vacuum filters, filter pressesor other expensive methods.

8. Anaerobic processes are not intended for controlling nutrients andheavy metals.

9. Anaerobic processes generate odorous gases such as hydrogen sulfide,and volatile organics. Accordingly, gases need to be collected, even atsmall treatment plants, and are usually treated and/or combusted.

10. Anaerobic reactors for wastewater treatment have deficient systemsfor water distribution, gas collection, and sludge separation. Foam andscum often are accumulated in the upper sections of anaerobic reactors.Poor mixing in low rate systems reduces the treatment efficiency.

11. Anaerobic systems for wastewater and sludge treatment have noprocess controls beyond temperature correction with heating and pHcorrection by reagents. Poor mixing in low rate processes makesautomation difficult because of a resulting random nature ofconcentrations distributions in the reactors.

12. Anaerobic reactors require a large area, because structural and costconsiderations limit the total reactor height to 6 to 9 meters. Specialegg-like shapes for avoiding grit accumulation are complex and costly toerect.

In summary, the above mentioned problems numbered 1 to 11 are related toa deficient sludge management strategy in prior art anaerobic wastewatertreatment systems, and problems numbered 9 to 12 are related todeficient designs of anaerobic reactors. These two fundamentaldeficiencies limit the use of anaerobic treatment systems and causeoperational problems in many of the systems already built.

The coupled anaerobic-aerobic systems have been developed and usedduring the past fifty years for treatment of concentrated industrialwastewater. These systems incorporate a separate anaerobic subsystem(functional section) with the final anaerobic clarifier and sludgerecycle, and aerobic subsystem separation and sludge recycle step. Onlyexcess aerobic sludge may sometimes be transferred to the anaerobicsubsystem. This system has important advantages as compared to aerobicsystems: high concentration waste can be treated, lesser quantities ofsludge are produced, and better removal of soluble and suspended solidorganics can be achieved.

However, anaerobic and aerobic functional sections in theanaerobic-aerobic systems are only mechanistically coupled. Sludges inthese sections do not interact: their make-up and properties abruptlychange from anaerobic to aerobic stage. The major disadvantages ofanaerobic-aerobic systems are as follows:

almost uniform sludge make-up and concentration along the major processzones (poor F/M ratios in various process zones), and poor diversity ofspecies in the sludge in each functional section;

operational difficulties in treating low concentration wastewater;

high sludge age and high degree of sludge stabilization in the aerobicsubsystem (low content of organics convertible to methane and low massand volume reduction in such conversion);

poor removal of suspended solids;

low process stability in response to dynamic overloading and toxicshocks;

low efficiency of degradation of poorly and slowly degradable and toxicorganics;

loss of volatile organics to the air in open facultative, anoxic, andaeration sections;

difficulties in removing nutrients (nitrogen and phosphorous).

Several modifications of biofiltration systems have been developed,including aerobic and anaerobic, with and without water recirculation, asingle, or multiple-stage system. Various lagoon systems have also beendeveloped. Most often the lagoon systems comprise a series of aerated ornonaerated sections. Hydraulic retention time in lagoons is very longand sludge recycle is not practiced. Processes in lagoons are usuallysimilar to those in ASP, but are not intensive and are less controlled.Some lagoons may have an anaerobic section, often followed with anaerobic sections. Such lagoons are similar to the anaerobic-aerobicsystems. Open anaerobic lelgoons produce odors. Large water volume inthe systems insures equalization of wastewater and sludge concentrationsand provides a substantial process stability. However, poor mixingcauses breakthroughs of poorly treated waste, and an overall low processefficiency. These systems are mechanically simple and require lowmaintenance. Many disadvantages of ASP and anaerobic-aerobic processeslisted above are also typical for biofilters, rotating biologicalcontractors, lagoon systems and various other modifications ofbiological wastewater treatment.

Sludges generated in wastewater treatment processes, for example inbiofiltration or activated sludge process, are usually directed foreither aerobic or anaerobic biological stabilization. Sludge thickeningmay precede biological stabilization. Methods of sludge thickeninginclude: gravity thickening in tanks designed as settling tanks,sometimes with gentle mixing; pressure air flotation; thermal gravitythickening/flotation thickening; vibratory filters; drum screens; andcentrifuges.

During biological stabilization, sludge is substantially mineralized andbecomes nonrotting; however, it retains a large proportion of water,which makes sludge disposal difficult. Accordingly, sludges are usuallydewatered and dried, which may be accomplished on drying beds--themethod preferred at smaller plants. Separate dewatering and drying areused at larger plants, the methods including vacuum filtration, filterpressing, centrifugation, etc. Separate methods of drying include dryingbeds, rotary drums, fluidized bed dryers, dryers with opposite jets,etc. Sometimes sludges are thickened, dewatered and dried withoutbiological stabilization, or a chemical stabilization is used instead.

Thermal gravity thickening, and thermal gravity/flotation thickeningshow significant advantages over other thickening methods. These methodsare described in the book Utilization of Wastewater Sludges, by A. Z.Evilevich and M. A. Etvilevich, Publishing House Stroyizdat, Leningrad(S. Peterburgh), 1988 (in Russian) and in Soviet Certificates ofInvention Nos.: 300420, 1971; 381612, 1973; 1118623, 1984. Advantagesinclude more rapid and more efficient separation (thickening) of sludgeparticles from water. A major disadvantage of these methods is in thatheating of the sludge prior to the separation is done by a heat carrier,for example steam, which requires additional complex equipment, heatexchangers or the like, and energy from an external sources (such asfuel). Sometimes flotation is not stable and portions of the sludge hangup in the mid depth or settle to the bottom of the flotation tank.Additionally, odor due to generation of hydrogen sulfide often occurs.

SUMMARY OF THE INVENTION

In the present invention, wastewater influent and conditioned anaerobicsludge are fed into an anaerobic reactor where they are well mixed. Thereactor effects removal from the water and at least partialtransformation of constituents of concern; then, the effluent isdischarged from the reactor and directed to a sludge separator forseparating the anaerobic sludge from the water. Optionally, a periodicbatch reactor (sequencing batch) can be used. The reactor volume, or afraction thereof, can be used as a sludge separator in the batchreactor. The water may be discharged in units for further treatment, orto the environment. The separated sludge is directed into a sludgeconditioner, and the bulk of the conditioned sludge is recycled in theanaerobic reactor. The balance of the sludge, equal to the sludge growthamount, is discharged to a sludge disposal or utilization facility.

The sludge conditioning of the present invention may include anaerobicconditioning, a combination of aerobic and anaerobic steps, chemicalconditioning, and a combination of chemical and biological conditioningsteps including aerobic and anaerobic steps and combinations thereof.Predominantly methanogenic sludge is formed in the sludge conditioner.

Clean anaerobic gases, virtually odor-free and free from hydrogensulfide, can be generated by the method of the present invention. Thesulfide toxicity in the reactors will be eliminated.

Two operation modes of the method are possible: complete and incompletetreatment. Complete treatment involves substantially total acidificationof soluble substrate in the feed material and substantially completemethanogenic conversion of fatty acids by recycling massively themethanogens from the sludge conditioner. Only traces of the originalsoluble organics and of fatty acids remain in the wastewater. Virtuallyall feed materials can be treated in less than 3 days. Incompletetreatment can be controllably achieved by providing deficient quantityof acidogens, thus, not all original soluble substrate is acidified; or,by recycling deficient amount of methanogens, thus leaving a sizablefraction of fatty acids in the effluent or by both, thus resulting innoticeable residual fatty acids and original organics in the effluent.

Deficient supply of acidogens can be insured by using short retentiontime in the reactor and by reducing recycle of acidogens from the sludgeseparator or sludge conditioner. Deficient supply of methanogens isprovided by controlling the recycle of the conditioned sludge.

A novel reactor for carrying out the method of the present inventioncomprises a vertical shell with an optional domed roof. The bottom partof the shell may be used for the sludge conditioning zone, while theupper part of the structure houses the reaction zone. Wastewaterinfluent is fed into the upper reaction zone, and a portion of thesludge from the lower conditioning zone is fed to the upper zone. Eachzone may be independently mixed. The reaction zone is a complete mixreactor with virtually the same concentrations of all constituents atany point in the reactor. The treated wastewater carrying residualpollutants can be transferred from the reaction zone to a sludgeseparator. Sludge from the sludge separator can be returned to thebottom of the structure in the sludge conditioning zone or the reactionzone. The treated separated water may be discharged from the system,while the gas generated in the reaction and sludge conditioning zones isdischarged to the atmosphere or, optionally, collected and evacuated atthe top of the structure.

In a sequencing batch reactor, the volume of the reactor, or a fractionof such volume, may be used to accommodate the sludge separation zone.Optionally, this zone may be provided with means for degassing thesludge and diverting the gas flow from the sludge separation means.Sludge separation means such as a centrifuge or a filtration device mayalso be used in sequencing batch reactors with sludge conditioning.

The present invention provides improved anaerobic-aerobic treatmentmethods by providing novel flow patterns of wastewater and sludges, andby cultivating sludges most appropriate for the concentration andcomposition of wastewater in a given process section. Cultivation ofappropriate sludges is accomplished by providing a broad range of sludgecompositions and properties. The present invention uses a combinedtreatment system with (1) a general counterflow of the biologicalsludges and wastewater being treated, (2) a high sludge concentration atthe head of the system where the organics concentration is also high,(3) a great diversity of sludge organisms in the systems and gradualchange in the biocenoses along the system, and (4) an alternatingexposure of wastewater constituents and metabolic products to variousfunctional groups of biological sludges. In such systems, the wastewaterconstituents are exposed to a broad range of environmental conditions:physical, chemical, and biochemical and physical-chemical actions due tothe availability of many organism types, enzymes, co-metabolizingspecies (vitamins, growth substances, steroids, nucleic acids, etc.), abroad ORP range, and favorable chemical make up.

Further improvement is provided by establishing functional process zoneswith specific biocenoses: anaerobic, facultative, anoxic, aerobic, andpolishing. A novel type of functional zone with simultaneous anaerobic,anoxic and aerobic activities is developed for the removal of variousclasses of organics, including biodegradable and recalcitrant and toxic,through oxidations and reductions in a wide ORP range. Biological andchemical pathways of nitrogen removal are employed in such functionalzones.

Yet further improvement is due to recirculation of treated or partiallytreated wastewater back to the upstream sections of the process andpassing down a fraction of biomass from the upstream sections of theprocess to the downstream locations, thus providing treatment of theoriginal wastewater constituents and metabolic products underalternating oxidation-reduction and enzymatic conditions. Such treatmentalso includes a thorough nitrogen removal.

Additional improvement is in applying to the treatment systems physicalactions, such as magnetic, ultrasonic, or radio frequencyelectromagnetic fields, physical-chemical actions, such as electrolyticaction, adsorption, coagulation-flocculation (includingelectrocoagulation), and chemical actions, such as addition of strongoxidants (H₂ O₂, ozone, Fe³⁺, nitrates, nitrites, and other oxyions) ortheir internal beneficial reuse. Addition of nutrients, such as nitrogenand phosphorous, and micronutrients, such as microelements and, ifneeded, biostimulators such as vitamins, steroids, folic acid, metalnaftenates and nucleic acids.

A further objective of the present invention is to provide a method andapparatus for sludge thickening which does not require energy fromexternal sources, and does not need complex equipment for sludge heatingand for sludge flotation. The method is also stable and efficient.Moreover, the method can be combined with sludge stabilization, and withsludge dewatering and drying.

The present invention is based on the ability of aerobic bacteria toconsume oxygen for oxidation of organics in the sludge. This is anexothermic process that causes the sludge temperature to rise. Theheating effect becomes greater when the concentration of organics in thesludge and the concentration of oxygen in the oxidizer are greater. Inany case, it is possible to bring the temperature of activated sludgeremoved from the bottom of clarifiers, or a mixture of activated sludgeand sludge from primary clarifiers to 60-70° C. with the use of air asthe oxidizer. In colder climates and at low concentrations of organics,oxygen or oxygen enriched air can be used as an oxidizer. Oxygenenrichment increases the available heat due to less heat loss from thenitrogen present in the air and with water vapors saturating off gases.Increasing of the sludge temperature by aeration will be herein referredto as bioheating.

As in heating with an external heat source, bioheating increases therate and the efficiency of sludge separation due to lower viscosity ofthe water phase. However, there is no need for additional energy orfuel, and there is no need for additional heating equipment.

An additional and novel step in the present invention involvescontrollable bioflotation, which is the process of sludge flotation bygas bubbles generated after the aerobic sludge has been exposed toanaerobic conditions. Under anaerobic conditions, gas is generated byacidogenic and methanogenic bacteria (methane and carbon dioxide),sulfate reducers (carbon dioxide and hydrogen sulfide), and denitrifyingbacteria (nitrogen). The process of gas generation and bioflotation canbe controlled by controlling the growth and activity of various groupsof organisms, or through sludge conditioning.

The process of bioflotation is well known, but improvements forcontrolling the process are provided herein. These improvements include,separately or in combination, the following:

1) Sludge is bioheated before bioflotation, which increases the processrate and insures bioflotation in colder climates. Bioflotation isachieved by subjecting the sludge to anaerobic conditions whereinmethane, carbon dioxide, and/or nitrogen are preferably formed. In someinstances, hydrogen sulfide may also be formed. These gases float up thesludge.

The anaerobic reaction step of the bioheated sludge can be conducted ona drying bed, and any presently known type of bed can be used. Duringthis reaction, the sludge is floated up leaving a clear water layer atthe bottom. Clear water rapidly filters through the drainage provided atthe bed. The floated layer of the thickened sludge subsides down to thebed surface and is kept there until dry.

Alternatively, the anaerobic step and flotation can be performed in aseparate flow-through reactor and separator (flotator). These steps canalso be performed in a batch reactor: first, anaerobic reaction iscarried out, followed by sludge flotation. After the thickened sludgeand water are separated, the sludge is directed to a dryer. Any dryerused for sludge drying can be used.

2) Nitrates and nitrites are generated from nitrogen sources (urea orammonia) or added to and mixed with the aerobically bioheated sludge, orimmediately after the bioheating step in order to promote, respectively,denitrification and sludge flotation. Nitrates accelerate the processdescribed in previous paragraphs.

3) The sludge flow is split into parallel aerobic bioheating andanaerobic digestion steps. In the anaerobic, step, long sludge ages aremaintained to cultivate denitrifying acidogenic and methanogenicbacteria. Methanogenic and denitrifying bacteria consume fatty acidsgenerated by the acidogenic organisms. At a longer sludge age,methanogenic and denitrifying bacteria deplete the fatty acids and otherorganic sources required for the growth of sulfate reducing bacteria.Accordingly, the growth of sulfur reducers is suppressed, the hydrogensulfide is generated in very small quantities, and the process can bekept substantially odor free.

The effluent sludges from both aerobic bioheater and anaerobicconditioner are mixed in the next process step. In this step, conductedwithout aeration, carbon dioxide, methane, and nitrogen are generated,form bubbles and float up the sludge particles. In a continuous process,the reaction in the mixed aerobic and anaerobic sludges is conducted ina separate reactor, while flotation is conducted in a separate settling(flotation) type tank. Alternatively, the reaction between aerobic andanaerobic sludges and flotation are conducted in a batch reactor whereina rapid mixing of predetermined portions of anaerobic and aerobicsludges is conducted first, followed by biological reaction with orwithout mixing, and by sludge flotation (during the biological reaction)without mixing or after the mixing is stopped. Such control strategyaccelerates bioflotation, insures process stability and high efficiencyin cold and warm climates, and eliminates the problem of odors.

Improvements to the bioflotation relate to sludge conditioning steps.They may be used in conjunction with wastewater treatment and sludgetreatment prior to thorough dewatering and drying.

The steps of reacting the mixture of the aerobic and anaerobic sludgescan be conducted on any conventional drying bed. During this reaction,the sludge is also floated up, leaving a clear water layer at thebottom. Clear water rapidly filters through the drainage provided at thebed. The floated layer of the thickened sludge subsides down to the bedsurface and is kept there until dry.

Yet another objective of the present invention is to provide at least apartial treatment of wastewater in the collection and transportationnetwork. Simultaneously, odorous and noxious gases, including hydrogensulfide and volatile organics, will be eliminated and pipe corrosioncaused by hydrogen sulfide and sulfuric acid in pipelines will beprecluded.

In the present invention, the wastewater is at least partially treatedwithin the collection and transportation network of pipes and channels.Predominately anaerobic treatment is used. Optionally, a combinedanaerobic-aerobic, aerobic, or biological and physical chemicaltreatment can be used within the network. The essence of the biological,chemical, and physical chemical treatment steps is already described inthe above section of this text. The final treatment, if needed, isprovided at the end-of-pipe treatment plants.

The sewer networks constitute, at least partially, the volume forcarrying out the reaction steps. As additional reaction volumes, wetpits of pump stations, and specially constructed tanks on the networkscan be used. These wet pits and tanks also provide a volume for theconcentration and the flow equalization. Due to equalization, theeffective hydraulic throughput capacity of sewerage pipes and treatmentworks may be increased, and the treatment stability at the treatmentplants may be improved.

The base version of the method includes spontaneous propagation ofacidogenic organisms in the pipe networks, conversion of at least aportion of biodegradable organics into fatty acids and other products ofthe initial digestion stages, generation of strongly methanogenic sludgeoutside of the pipe networks and feeding it in the upstream stretches ofthe sewer network, rapid conversion of the fatty acids to methane,depriving the sulfur reducing organisms of food (fatty acids) by thesaid rapid conversion and consumption by the methanogens. These processsteps provide at least partial removal of organics through theirconversion to mostly carbon dioxide and methane, eliminating formationof hydrogen sulfide and greatly reducing volatilization of organics.During this treatment, wastewater does not become acidified and sulfuricacid is not formed. Accordingly, corrosion is largely eliminated.

Methanogenic sludge can be generated in sludge conditioners at theend-of-pipe treatment plant and delivered to the upper reaches of thenetwork system by sludge pipelines, or transported in tanks. Also,anaerobic reactors for generating methanogens using wastewater organicsas food can be installed in the upper reaches of the pipe networks. Athird possibility would be the use of solid or liquid municipal orindustrial waste or other organic feedstock for generating methanogens.In the latter case, the methane generating reactors may be installedeither on the pipe network system, or somewhere else.

Yet another objective of the present invention is to control odors atwastewater treatment plants. This can be achieved by installing ananaerobic treatment systems with a sludge conditioner at the head of thetreatment plant (before screens). This unit can be fed with rawwastewater and will produce odor-free gases. Optionally, means for sizereduction of the coarse admixtures can precede the anaerobic unit. Gritchambers will not be required, because the anaerobic unit will collectthe grit in the inverted pyramids at the bottom, from where it is easilyremovable together with the excess sludge.

The unifying idea in the present invention is based on coupling theanaerobic reaction and various sludge conditioning steps. Such couplingis provided in an optimal manner and results in new and nonobviouseffects. For example, proper sludge management allows one to buildodor-free, open, true anaerobic reactors or control complete orincomplete treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention willbecome apparent from consideration of the following specification, whentaken in conjunction with the accompanying drawings in which:

FIG. 1 is a flow chart of an anaerobic system made in accordance withthe present invention, with a sludge conditioner;

FIG. 2 is a flow chart of a multichannel sludge conditioner for use inthe system of FIG. 1;

FIG. 3 is a modified form of a multichannel sludge conditioner;

FIG. 4 is a flow chart of a sludge conditioner comprising parallelanaerobic and aerobic steps;

FIG. 5 is a flow chart of a sludge conditioner comprising sequentialaerobic and anaerobic steps;

FIG. 6 is a flow chart of a multiple stage anaerobic system with sludgeconditioners in each stage;

FIG. 7 is a flow chart of a multiple stage anaerobic system with sludgeconditioners in each stage, the second stage conditioner including anaerobic process step;

FIG. 8 is a vertical cross-sectional view of a structure made inaccordance with the present invention for anaerobic treatment ofwastewater;

FIG. 9 is a horizontal cross-sectional view of a bottom part of apolygonal structure similar to that shown in FIG. 8;

FIG. 10 is a horizontal cross-sectional view of a bottom part of acircular structure similar to that shown in FIG. 8;

FIG. 11 is a horizontal cross-sectional view of a bottom part of asquare structure similar to that shown in FIG. 8;

FIG. 12 is a vertical cross-sectional view similar to FIG. 8 and showinga modification thereof;

FIG. 13 is a vertical cross-sectional view showing another modificationof the structure shown in FIG. 8; FIG. 14 is a vertical cross-sectionalview showing yet another modification of the structure shown in FIG. 8;

FIG. 15 is a top plan view of an open structure for use in the presentinvention;

FIG. 16 is a cross-sectional view taken along the line 16--16 in FIG.15;

FIG. 17 is a vertical cross-sectional view showing a modification of thedevice shown in FIG. 16;

FIG. 18 is a cross-sectional view of a sequence batch reactor takenalong the line 18--18 in FIG. 19;

FIG. 19 is a top plan view of an open structure of a sequencing batchreactor showing a modification of the device illustrated in FIG. 18;

FIG. 20 is another modification of the structure shown in FIG. 18;

FIG. 21 is yet another improvement of the structure shown in FIG. 18;

FIG. 22 is another alternative of the sequencing batch reactor;

FIG. 23 is a sequencing batch reactor with a gravity separator built in;

FIG. 24 is a flow chart showing a wastewater treatment plant including acoupled an anaerobic treatment stage and an aerobic treatment stage;

FIG. 25 is a top plan view of a splitter box for use with the presentinvention;

FIG. 26 is a cross-sectional view taken along the line 26--26 in FIG.27;

FIG. 27 is a cross-sectional view taken along the line 27--27 in FIG.25;

FIG. 28 is a flow chart showing an anaerobic block with a reactorcomprising multiple sequential cells;

FIG. 29 is a cross-section of a reactor with multiple sludgecompartments and multiple reactor cells;

FIG. 30 is a flow chart of a system for sludge thickening made inaccordance with the present invention, with sludge bioheating andbioflotation;

FIG. 31 is a modified form of the system for sludge thickeningcomprising parallel aerobic bioheating and anaerobic sludge conditioningsteps followed by a bioflotation step;

FIG. 32 is a schematic diagram of a system for sludge thickening,dewatering and drying comprising a bioheating unit and a drying bedfunctioning as sludge flotation, thickener and a drying means;

FIG. 33 is a schematic diagram of a system for continuous sludgethickening comprising a bioheating means, an anaerobic reactor and asludge/water separator;

FIG. 34 is a schematic diagram of a system for periodic (batch) sludgethickening comprising a means for bioheating and a combined anaerobicreactor and sludge/water separator;

FIG. 35 is an elevational view of a combined anaerobic-aerobic processwith a zone of a simultaneous presence of aerobic and anaerobic sludge;

FIG. 36 is another form of apparatus similar to FIG. 35 but having theaerobic zone disposed above the anaerobic zone;

FIG. 37 is a plan view of the anaerobic section of the apparatus shownin FIG. 36;

FIG. 38 is an apparatus for gas treatment;

FIG. 39 is a schematic diagram showing the basic arrangement of thewastewater management system with the delivery of the conditionedanaerobic sludge from a wastewater treatment plant;

FIG. 40 is a schematic diagram showing a modified form of the system ofFIG. 39, the methanogenic sludge generating reactors being installed atthe upper reaches of the wastewater networks and using wastewaterorganics as a source of food;

FIG. 41 is a schematic diagram showing a modified form of the system ofFIG. 39, the methanogenic sludge generating reactors being installed atthe upper reaches of the wastewater networks and using organics of solidor liquid wastewater as a source of food;

FIG. 42 is a schematic of a use of the anaerobic treatment system at thefront end of the treatment plant for removing grit, screening, organicsconversion and sludge stabilization and thickening;

FIG. 43 is a schematic of an automatic control system for apparatusshown in FIG. 8;

FIG. 44 is another schematic of an automatic system for apparatus shownin FIG. 8;

FIG. 45 is a schematic of an automatic control system for apparatusshown in FIG. 18; and,

FIG. 46 is a schematic of an automatic control system for apparatusshown in FIG. 35.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now more particularly to the drawings, and to thoseembodiments of the invention here chosen by way of illustration, in FIG.1 there is an anaerobic reactor 1 with an influent conduit 9 and a line10 connecting the reactor 1 to a sludge separator 2. The sludgeseparator 2 is connected to a sludge conditioner 3 by a line 12, and aline 11 is provided from the sludge separator for the liquid effluent. Aline 13 connects the sludge conditioner 3 to the anaerobic reactor 1,and a line 14 is provided to discharge sludge to the environment, orotherwise remove it from the present processing system.

The sludge conditioner 3 optionally includes; a plurality of inlets 111,112, 113, 114 and 115 for feeding nutrients, liquid or solid organics,sulfur bearing reagents, powdered activated carbon, oxyions includingnitrites and nitrates, vitamins, biostimulators and microquantities ofspecific pollutants respectively into the sludge conditioner 3.Alternatively, similar inlets can be provided in the reactor 1 forfeeding the reagents and micropollutants directly into the reactor.

In operation, wastewater influent and recycled sludge (second anaerobicsludge) are fed via lines 9 and 13 into the anaerobic reactor 1. Thewastewater influent contains soluble and insoluble organics, and someconstituents of wastewater may be poorly or slowly biodegradable, ortoxic. The recycled sludge carries anaerobic microorganisms in bioflocsand/or granules. The sludge also includes enzymes produced by themicroorganisms, alkalinity due to the bicarbonates and specific reagentsadded, or produced in the course of sludge conditioning. In reactor 1,the organic matter fed with the wastewater undergoes transformations.First, there is partial solubilization and coagulation-flocculation ofsuspended solids, so that the remaining suspended solids can beseparated from the mixed liquor in the sludge separator. Second, thereis conversion of the soluble organics by acidogenic organisms into fattyacids, followed by a conversion of fatty acids by methanogenic organismsinto methane. Both acidogenic and methanogenic organisms (the firstanaerobic sludge) will also produce carbon dioxide. Additionally, afraction of incompletely converted organics, including poorly and slowlysoluble and toxic organics, will be adsorbed by the biological mass inthe reactor. These adsorbed organics will be separated from the mixedliquor in the sludge separator, and will not be present in the effluentfrom the anaerobic process stage.

The acidogenic microorganisms are largely grown in the anaerobic reactorand survive to a small degree in the sludge conditioner, while themethanogenic organisms (the second anaerobic sludge) are cultivatedsubstantially in the sludge conditioner.

For use as the anaerobic reactor, either a suspended growth (mixedreactors) or an attached growth reactor, or a combination of the two,can be used. In the suspended growth reactor, the bulk of themethanogenic sludge is brought from the sludge conditioner. Depending onthe conditioning and recycle of acidogenic and methanogenic organisms,the process rate may vary from low to high, an either complete orincomplete treatment may be provided. As an attached growth reactor,upflow or downflow packed media reactor, or a suspended sludge blanketreactor, with or without support media (particles of sand, crushedceramsite, or granulated activated carbon) can be used. In the attachedgrowth reactor, a partial retention and accumulation of methanogenicsludge occurs in the reactor itself. The rest of the methanogenic sludgeis brought from the sludge conditioner.

Mixed liquor from the anaerobic reactor, with the first anaerobicsludge, is transferred through the line 10 to the sludge separator 2.The sludge can consist of flocculent or granular particles or both. Thesludge separation step can be accomplished in a gravity separator(settling tank, clarifier, suspended sludge blanket clarifier, etc.), ina filtration device (granular media filters, screens, membranes, etc.),centrifuges, or other means for solid-liquid separation. Theanaerobically treated wastewater is evacuated from the sludge separator2 via line 11, and the separated sludge is transferred to the sludgeconditioner 3 via the line 12.

In the sludge conditioner 3, the first anaerobic sludge is treated inaccordance with particular requirements of the system. Sludge in thesludge conditioner constitutes only a fraction of the wastewaterinfluent by volume. Accordingly, a very long retention time in thesludge conditioner (weeks to months) is possible at a comparativelysmall volume of the sludge conditioners. Sludge conditioners may be asingle mixed tank, or a series of tanks, or other combinations asdescribed later. The sludge conditioner 3 may be an anaerobic process,or a combination of anaerobic and aerobic biological processes, andchemical and physical chemical processes.

In the course of anaerobic treatment in the sludge conditioner, theflocculated, suspended solid particles are solubilized, and the productsof solubilization are decomposed into fatty acids, and further intomethane and carbon dioxide. The organics adsorbed in the sludge in theanaerobic reactor, including slowly and poorly degradable and toxicmaterials, are largely degraded over a long solids retention time.

Sludge recycle from the sludge conditioner 3 brings controllably to theanaerobic reactor 1 a substantial amount of alkalinity so that, incombination with the acid consumption by the recycled methanogens, thepH in the reactor is well buffered with little or no alkalinic reagentrequirements. The total retention time in the novel system, on theinfluent flow basis, may be from several hours to under 3 days ascompared to 3 to 15 days and longer in prior art suspended growthsystems.

Sulfates, nitrates, nitrites and chromates and other oxyions arecontrollably reduced to sulfides, nitrogen, and trivalent chromium.These processes may occur in the anaerobic reactor or in the sludgeconditioner, or both. Sulfides will precipitate heavy metals, forexample, copper, mercury, zinc, and chromium.

Since the bulk of sulfides can be associated with calcium, magnesium,and iron, addition of sulfur-bearing species, sulfur, sulfuric acid,polysulfides, etc., can be provided in the anaerobic reactor or in thesludge conditioner (via inlet 113). Reduction of nitrates and nitrites(for example, recycled to the anaerobic reactor with aerobically treatedand nitrified water) results in removal of a nutrient, nitrogen.

The degree of sulfate reduction is controlled by the availability of thefatty acids, which are the carbon source for the sulfate reducingorganisms. Massive recycle of methanogens from the sludge conditionerresults in rapid consumption of fatty acid. Accordingly, sulfatereducers are deprived of carbon source and their growth is suppressed.Small quantities of generated sulfides react with sulfate to forminsoluble elementary sulfur.

If wastewater influent has substantial concentrations of poorly, orslowly degradable organics, for example certain surfactants, or toxic,partially degradable organics, for example methylene chloride orchloroform, powdered activated carbon can be added to the reactor or tothe sludge conditioner (via inlet 114) in order to adsorb theseconstituents and retain them in the system, mainly in the sludgeconditioner, for a longer time so these constituents will besubstantially degraded.

In the case of toxic slugs in the wastewater influent, the sludge in theanaerobic reactor becomes poisoned and inactivated. This may happen inany reactor type, without exception. In the present method with thesludge conditioning step, the sludge stored and undergoing theconditioning in the sludge conditioning step is off line and is notpoisoned by the toxic slug of wastewater; accordingly, only ashort-duration process upset may occur.

The conditioned sludge from the conditioner 3 is fed into the anaerobicreactor 1 via line 13. A portion of the stabilized and conditionedsludge (concentration from 80-90 to 150-180 g/l), which is equal to theamount grown and accumulated over a given period of time, is dischargedvia line 14 over the same period of time.

FIG. 2 illustrates one form of sludge conditioner 3 which comprisesmultiple parallel anaerobic compartments designated at 4a to 4e, with amanifold 12 for sludge infeed and a manifold 13 for sludge outfeed. Aline 14 is provided for sludge discharge, either to the environment orto another processing system.

The sludge conditioning is arranged as a multichannel system withparallel compartments, each compartment being operated in a semibatchmode. For example, sludge from the compartment 4e is recycled to theanaerobic reactor 1, while all other compartments are in the batch mode,conditioning the sludge without any sludge exchange with the reactor 1.The compartments are in a queue, and can be controllably put in therecycle mode for a specified period on a sequential basis (for example,at a recycle period equal to one week per compartment, the totalturnaround period for five compartments will be five weeks, or thesludge age increment due to the sludge conditioner is five reeks).

Alternatively, various compartments may be used for various conditioningmethods. For example, some compartments can be aerobic, othersanaerobic.

FIG. 3 shows another sludge conditioner 3, this conditioner comprisingmultiple parallel anaerobic compartments 5a, 5b and 5c. The differentcompartments have different volumes, the compartment 5c being a by-passwith a zero volume. The manifold 12 provides for sludge infeed, manifold13 for sludge outfeed, and pipe 14 for sludge discharge.

In this conditioner, the sludge conditioning step involves substeps ofcontinuous sludge conditioning in parallel chambers of different sizes.Such treatment permits cultivation of the combined recycle sludge with abroad range of sludge age, and various groups of organisms. For example,the short-time compartment 5c will support the growth of acidogenicorganisms, the medium-time compartment 5b will provide good growth oforganisms responsible for solubilization of suspended solids, and thelong-time compartment 5a will support methanogenic growth. A specialcompartment for growing sulfate reducers and generating sulfides can beprovided. Such a compartment may be fed with a carbon source (includingwastewater) and a sulfur source such as sulfates. Sulfides formed inthis compartment can be used for removal of heavy metals fromwastewater. A modification of this conditioner may be a channel with adistributed infeed along the length and a single outfeed at the channelend, so that different infeed portions of the conditioned sludge havedifferent ages. Sludge composition may differ from that in amultichannel conditioner.

FIG. 4 shows a sludge conditioner 3 comprising an anaerobic compartment6 and an aerobic compartment 7, the two compartments being connected bylines 26 and 27 for sludge transfer between them. The line 12 is forsludge infeed, 13 for outfeed, and 14 for sludge discharge. There is aline 28 for feeding oxygen, air, or enriched air supply into the aerobiccompartment 7.

The sludge conditioner 3 is subdivided into an anaerobic compartment 6and aerobic compartment 7. A portion of the sludge from the anaerobiccompartment 6 is fed to the aerobic compartment 7, and the aerobicallytreated sludge is returned to the anaerobic compartment 6. In theaerobic compartment 7, some organics, especially those resistant to theanaerobic transformations, will undergo aerobic destruction. Because theaerobic processes have greater sludge yield, the mass of sludge grown inthe system will increase as compared to anaerobic processes. This willcreate mass capable of adsorbing organic and inorganic constituents inthe anaerobic reactor 1, and removing respective pollutants from thewastewater influent.

Aerobic treatment is also one means for raising the temperature of thesludge in the sludge conditioner. The increased temperature increasesthe process rate and the degree of organics destruction. Moreover, theorganisms and enzymes generated in the heated sludge conditioner will beactive, although not self sustaining, in the anaerobic reactor. Thiswill be useful for treatment of wastewater that is at low temperatures.Alternatively, the heating could be achieved by the use of conventionalsludge heating.

FIG. 5 shows a sludge conditioner 3 comprising an aerobic compartment 7and an anaerobic compartment 6 connected in series by a line 29. Ifdesired, there may be a line 8 for by-passing the aerobic compartment 7and directing the sludge into the anaerobic compartment 6. As in thepreviously described embodiments, there is an infeed line 12 and anoutfeed line 13. The discharge line 14 optionally by-passes thecompartment 7 and immediately discharges the sludge from the system.

In the device of FIG. 5, a portion of the sludge from the sludgeseparator 2 is fed to the aerobic compartment 7. The aerobically treatedsludge is subsequently transferred to the anaerobic compartment 6. Thebalance of the sludge from the sludge separator is by-passed directly tothe anaerobic compartment 6. In the aerobic compartment 7, someorganics, especially those resistant to the anaerobic transformations,will undergo aerobic destruction. Because the aerobic processes havegreater sludge yield, the mass of sludge grown in the system willincrease as compared to the use of anaerobic processes only. This willcreate mass capable of adsorbing organic and inorganic constituents inthe anaerobic reactor 1 and removing respective pollutants from thewastewater influent. As is mentioned above, the aerobic treatment willalso increase the temperature of the sludge.

In FIGS. 1 to 5, multiple sludge separators can be used. For example,the same type and size separators may be provided in each sludgeconditioning channel, or different type and size separators can be usedin different channels. One sludge separation device may be used forseveral sludge conditioning channels. Various types of sludgeconditioners can be connected in series or parallel.

Referring now to FIG. 6 of the drawings, a multiple stage anaerobicsystem with sludge conditioning is illustrated. There is a first stageanaerobic reactor 1a, a sludge separator 2a, and a sludge conditioner 3aarranged as discussed in connection with FIG. 1, and the lines arenumbered as in FIG. 1 with a suffixes. In the system of FIG. 6, however,the effluent line 11a is connected to the second stage of the system.The second stage of the system is also like the system of FIG. 1, andthe parts are numbered the same, with a b suffix. It will be seen thatthe discharge 14b returns to the first stage anaerobic reactor 1a.

In this embodiment of the invention, the wastewater influent issubjected to treatment in a multiple stage anaerobic system with sludgeconditioning. The wastewater influent is fed into the anaerobic reactor1a via line 9 (optionally, a portion of the influent may be fed to thesecond stage reactor 1b), and the influent undergoes controllableincomplete treatment as previously described. The mixed liquor is thentransferred to the sludge separator 2a via line boa. From the sludgeseparator 2a, the sludge is directed through the line 12a to the sludgeconditioner 3a, where it undergoes the transformations previouslydescribed. The conditioned sludge is partially recycled to the anaerobicreactor 1a through the line 13a, and the balance is discharged via line14a. The wastewater effluent from the sludge separator 2a is fed in theanaerobic reactor 1b via line 11a, where it undergoes the controllablecomplete treatment as previously described; then, the mixed liquor istransferred to the sludge separator 2b via line 10b. From the sludgeseparator 2b, the sludge is directed through the line 12b to the sludgeconditioner 3b, where it undergoes the transformations previouslydescribed. The conditioned sludge is partially recycled to the anaerobicreactor 1b by the line 13b, and the balance is transferred to the firstprocess stage anaerobic reactor 1a via line 14b.

The advantage in the use of two or more stages is in the effect of"counterflow" of the sludge and the wastewater. In particular, thepoorly degradable and especially poorly adsorbable organics will bepartially removed in the first process stage. The sludge in the sludgeconditioner will substantially transform the poorly degradable andpoorly adsorbable organics; however, due to the nature of theseorganics, the residual quantity of them will be recycled back to thefirst stage anaerobic reactor, and therefore will be lost from the firststage sludge separator. These residual quantities will be additionallyremoved in the second process stage. This advantage is also veryimportant for the removal of heavy metals and specific pollutants. In aone-stage process, the sludge circulating in the system is loaded withheavy metals, so that the new portions of the wastewater influent bringnew quantities of heavy metals in contact with sludge alreadysubstantially saturated with heavy metals. Such sludge has lowaccumulation capacity and cannot hold additional heavy metals. In thetwo or more stage process, the first stage sludge removes the bulk ofheavy metals. In the second stage, much "cleaner" sludge scavenges theresidual heavy metal admixtures.

FIG. 7 illustrates another multiple stage anaerobic system with sludgeconditioning, this system being the system of FIG. 6 with a sludgeconditioner as shown in FIG. 4. The parts are numbered as in FIG. 6 andin FIG. 4. It will be seen that the effluent line 11a leads to thesecond stage reactor 1b, and the discharge line 14b from the secondstage leads to the line 12a for input to the conditioner 3a. Other partsand connections are as previously discussed.

In operation of this embodiment, the wastewater influent is subjected totreatment in a multiple stage anaerobic system with sludge conditioning.The wastewater influent is fed into the anaerobic reactor 1a via line 9,where it undergoes the incomplete treatment as previously described;then, the mixed liquor is transferred to the sludge separator 2a vialine 10a From the sludge separator 2a, the sludge is directed throughthe line 12a to the sludge conditioner 3a, where it undergoes thetransformations previously described. The conditioned sludge ispartially recycled to the anaerobic reactor 1a by the line 13a, and thebalance is discharged from the system via line 14a.

The wastewater effluent from the sludge separator 2a is fed into theanaerobic reactor 1b via line 11a where it undergoes the treatmentpreviously described, then the mixed liquor is transferred to the sludgeseparator 2b via line 10b. From the sludge separator, the sludge isdirected through line 12b to the sludge conditioner 3b, where itundergoes the transformations previously described. The conditionedsludge is partially recycled to the anaerobic reactor 1b by the line13b, and partially fed via line 26 into the aerobic conditioner 7. Aportion of the aerobically conditioned sludge is returned to theanaerobic conditioner 3b, and the balance is transferred to the firstprocess stage anaerobic sludge conditioner 3a via line 14b. Theadvantages of the two or more stage arrangement have been discussedabove.

Referring to FIGS. 8, 9, 10, and 11, there is shown a combined structurefor anaerobic reactor and sludge conditioner. The structure consists ofa polygonal (FIG. 9), cylindrical (FIG. 10), or square (FIG. 11)vertical shell 35 with an optional domed top 37. The domed top may be apyramid, or a cone, or other similar shape. The top 37 then mounts a gascollection section 33, and a gas discharge pipe 34. The inside bottompart of the structure has a pyramidal or conical shape. The bottom partaccommodates the sludge conditioner to constitute the sludgeconditioning zone, while the upper part is for the anaerobic reactor toconstitute the anaerobic reactor zone.

Optionally, the lower part of the structure is separated into multiplecompartments 4 (FIGS. 9, 10 and 11) by vertical walls 36. A centralconnection element 39 may be also provided as shown in FIGS. 8, 9 and10. Pyramidal bottom 38 is provided in each sludge conditioningcompartment 4, and each compartment 4 is provided with outlet pipes 13and 31, and a pump 32 as means for moving the sludge to effect mixing.

The upper part of the structure may be separated into multiplecompartments by extending some or all of the partitions 36 upward intothe gas collection section 36 above the liquid level.

Lines 9 for wastewater influent and 10 for discharge of the anaerobicmixed-liquor are provided in the upper part of the structure. Pipes 13and pumps 32 are provided for moving the sludge between the sludgeconditioning zones 4 (or a single zone 4) and the reactor zone 1. Pipes12 and 14 are provided in the sludge conditioning compartments 4 fortransferring the sludge from a sludge separator to the sludgeconditioning zones 4 and for discharging stabilized excess sludge fromthe sludge conditioning zones 4.

Optionally, sludge from the sludge separator can be returned to thereaction zone 1, for example, through additional connections to pipes 13or 9. In such a case, the structure corresponds to a combination of flowcharts shown in FIGS. 2 and 3.

In operation, the wastewater influent is fed into the reaction zone 1via line 9. Conditioned sludge is fed from one of the multiple sludgeconditioning zones 4 (or from a sole conditioning zone) into thereaction zone 1 by one of the pumps 32, via lines 213. Sludge andwastewater in the reaction zone 1 are mixed by either gases generated inthe reaction zone and in the sludge conditioning zones 4, or by a mixingdevice (propeller mixer, circulating pump, gaslift, etc.). The gasesgenerated in the apparatus will flow up in the gas bell 33 to beevacuated via the pipe 34. A portion of the sludge in the mixed liquorin the reaction zone 1 settles down into the sludge conditioning zones4. The remaining sludge is discharged through the pipe 10 with the mixedliquor from the reaction zone 1 to a sludge separation device; and,after separation from the treated water the sludge is returned to asludge conditioning zone 4. Sludge in the conditioning zones 4 iscontinuously or periodically mixed by mixing devices. Circulation pumps32 and lines 213 and 31 are one example of mixing means. A propellermixer, or a jet pump can also be used. A mixing device in the sludgeconditioning zone in a combined structure as shown in FIG. 8 should notproduce significant uncontrollable sludge transfer from the sludgeconditioning zones 4 to the anaerobic reaction zone 1. Periodically orcontinuously, a portion of the stabilized conditioned and thickenedsludge is discharged from the system via line 14. Grit, present in thewastewater influent will settle and accumulate at the pyramidal bottomin each compartment 4. In such system grit will be easily removed withthe sludge discharge. Various previously described reagents, powderedactivated carbon, liquid and solid organics can be fed into the systemeither with the wastewater influent via line 9, or through lines 13 withthe sludge return after the sludge separator.

Optionally, the upper reaction zone 1 is separated into multiplecompartments by extended upward walls 36. Each reaction compartment isassociated with the fixed sludge conditioning zones. For example, atotal of two reaction zones are associated with eight conditioningzones, four conditioning zones per reaction zone. The groups of reactionand conditioning zones are connected sequentially, and counterflow ofsludge is provided as previously described.

When the apparatus of FIG. 8 is used for sludge digestion, sludge is fedinto the reaction zone and is inoculated with acidogens present andgrowing in this zone and with methanogens mostly pumped fromcompartments 4. A partially digested sludge settles from zone 1 tocompartments 4, wherein the biological conversions are completed. Theeffluent from zone 1 is directed to a sludge separator, for example, acentrifuge or a gravity thickener. The fugate or the supernatant arereturned to the water treatment train, while the sludge is fed again tothe apparatus shown in FIG. 8. Treated sludge is discharged fromcompartments 4 of this apparatus in a thickened form at a much higherconcentration than in conventional digestors. Due to conditioning of thesludge and its thickening, the process stability, rate, and loadings perunit volume greatly increase as compared to conventional digestors.

Referring to FIG. 12, there is shown an alternative combined structurefor anaerobic reactor and sludge conditioner. This structure is similarto the above described arrangement, but with a few changes.

Lines 9 for wastewater influent and 10 for the anaerobic mixed liquorare connected to the sludge circulation pipes 313 and 31. Pipes 313 andpumps 32 are provided for moving the sludge between the sludgeconditioning zones 4 and the reactor zone 1. Pipes 12 and 14 areprovided for feeding the sludge from a sludge separator to the sludgeconditioning zones 4 and for discharging the excess sludge.

In this arrangement, the wastewater influent is fed via lines 9 and 313.Circulation may be assisted in the selected sludge conditioning zone 4by the pump 32; and, such circulation assists also in the reactionzone 1. A suspended sludge blanket is formed in the selected sludgeconditioning zone 4, and for the period of selection the selected sludgeconditioning zone becomes a part of the reaction zone. Sludge andwastewater in the reaction zone 1, and the selected sludge conditioningzone 4, are kept in the fluidized state by the use of the pump 32, andadditionally mixed by gases generated in the reaction zone 1 and in thesludge conditioning zones 4. The gases generated in the apparatus flowup into the gas bell 33 and are evacuated via pipe 34. A portion of thesludge in the mixed liquor in the reaction zone 1 settles down into thesludge conditioning zones 4 which are not selected at the time. Theremaining sludge is discharged with the mixed liquor from the reactionzone 1 to a sludge separation device through the pipe 10; and, afterseparation from the treated water, is returned to a sludge conditioningzone 4. Sludge in the conditioning zones 4 is mixed as was discussedabove.

Referring next to FIG. 13, there is shown another variation of thecombined structure for anaerobic reactor and sludge conditioner. Again,the structure is similar to that shown in FIG. 8, but with some changes.

In FIG. 13, there is an enlarged central connection element 39 with anextension section 40 protruding through the gas collection section 33.The volume inside the element 39 and extension section 40 optionallycomprise the aerobic section 7 of the sludge conditioner. Section 7 isprovided with a pipe 28 for air, or oxygen, or oxygen enriched air.Alternatively, the volume inside the element 39 and section 40 can beused for generating sulfides, and pipe 28 may be used for feeding asource of sulfur, for example, aluminum sulfate. Pyramidal bottom 38 isprovided in each sludge conditioning compartment. Each compartment isprovided with pipes 13 and 31 and a pump 32 as means for sludge mixing,and also with pipes 43 for transferring the anaerobic sludge to theaerobic sludge conditioning section 7. Pipes 41 with valves 42 connectthe upper part of the aerobic section 7 with each anaerobic section 4.

Lines 9 for wastewater influent and 10 for the anaerobic mixed liquorare provided in the upper part of the structure. Pipes 13 and pumps 32are provided for moving the sludge between the sludge conditioning zones4 and the reactor zone 1. Pipes 12 and 14 are provided for feeding thesludge from a sludge separator to the sludge conditioning zones and fordischarging the excess sludge from the sludge conditioning zones.

It will be understood that most of the operation of this embodiment isthe same as the embodiment shown in FIG. 12, so the description will notbe repeated. The difference, however, is that a portion of the sludge ina selected sludge conditioning zone 4 is transferred via pipe 43 intothe aerobic sludge conditioning zone 7 and aerated with air, or oxygen,or oxygen-enriched air supplied through the pipe 28. Aerobically treatedand heated sludge is transferred back to the selected zone 4 by openinga valve 42 on line 41. Various lifting means can be used fortransferring the sludge between the selected anaerobic zone 4 and theaerobic zone 7. In FIG. 13, the transferring means is an airlift, whichalso accomplishes the aeration in the central well 39 and the standpipe40. Alternatively, a pump can be used for the sludge transfer betweenzones 4 and 7.

Since sulfides are oxidized into sulfates in the aerobic zone 7, heavymetals become soluble. They can be removed from the system with a smallamount of water by removing a portion of water from the aerobic sludge.Metals can be reduced to an even smaller volume by using known methods,and water virtually free of metals may be returned to the water train.Periodically or continuously, a portion of the conditioned sludge isdischarged from the system via line 14. Various previously describedreagents, powdered activated carbon, or liquid and solid organics can befed into the system either with the wastewater influent via line 9, orthrough lines 13 with the sludge return after the sludge separator.

An alternative operation of this apparatus with all baffles 36 extendedupward and inside the gas collection means 33 can be as follows: some"total height" zones will be operated at maximum flow while others areoperated at reduced flow or zero flow. All zones are operated inparallel as separate reactors with the time clock change in sequencingof the sections operated at maximum, reduced and zero flows. Sludge insections with less than maximum flow is being conditioned.

Yet another alternative operation of this apparatus is with the use ofthe element 39 and section 40 for sulfides generation. A sulfur sourcesuch as aluminum sulfate, and organics such as wastewater are fed viapipe 28 into anaerobic environment in the element 39. As in conventionalanaerobic reactors, hydrogen sulfide is generated. Liquid from thisvolume bearing hydrogen sulfide is brought to the reaction zone 1 viapipes 41, wherein heavy metals are precipitated. Metal sulfides remainwith the anaerobic sludge. Aluminum ions are used up to precipitatephosphorus, which also remains in the sludge.

Another variation of the combined structure is shown in FIG. 14. Again,the shape may be as shown in FIGS. 9, 10 or 11 and discussed above. Inthis embodiment of the invention, the outer shell 35 of the structure isextended upward to a level above the liquid level in the gas collectionsection 33. The space above the cone 37, separated by the extended shell35, houses the sludge separation zone 2. The base of the top cone 37 hasa diameter smaller than the diameter of the outer shell 35 so that acircular opening 64 is formed between the top cone 37 and the shell 35.An inclined circular baffle 61 is provided for gas collection in theinner space along the structure shell 35. Gas pipes 62 connect the gasspace under the baffle 64 with the gas space under the cone 37. A watercollection trough 63 with an influent pipe 11 is positioned at the waterlevel in the sludge separation zone 60.

The lower portions of the device are the same as in FIG. 8, and thedescription will not be repeated.

In operation of this embodiment, the wastewater influent is fed into thereaction zone 1 via line 9. Conditioned sludge is fed from one of thesludge conditioning zones 4 in the reaction zone 1 by one of the pumps32 via lines 213. Sludge and wastewater in the reaction zone 1 are mixedby either gases generated in the reaction zone and in the sludgeconditioning zones 4, or by a mixing device such as a propeller mixer,circulating pump, gaslift, etc. The gases generated in the apparatuswill flow up into the gas bell 33 and will be evacuated via pipe 34.Gases collected under the baffle 61 are directed beneath the cone 37 bypipes 62. A portion of the sludge in the mixed liquor in the reactionzone 1 settles down into the sludge conditioning zones 4. The remainingsludge is discharged with the mixed liquor from the reaction zone 1 to asludge separation zone 2 through the opening 64; and, after separationfrom the treated water, is returned through the same opening 64, back tothe anaerobic reaction zone 1 and ultimately to the sludge conditioningzones 4. The gravity-clarified water in the sludge separation zone 2 iscollected in the trough 63 and discharged from the system via pipe 11.Scum removal means, means for forced sludge transfer to the sludgeconditioning zones 4 instead of the reaction zone 1, and other availableoptions may be provided. Sludge in the conditioning zones 4 iscontinuously or periodically (for example, on a time clock basis) mixedby mixing devices such as the circulation pumps 32 and lines 213 and 31.Alternatively, a propeller mixer, or a jet pump can be used. A mixingdevice in the sludge conditioning zone in a combined structure as shownin FIG. 14 should not produce significant, uncontrollable sludgetransfer from the sludge conditioning zones 4 to the anaerobic reactionzone 1. Periodically or continuously, a portion of the conditionedsludge is discharged from the system via line 14. Various previouslydescribed reagents, powdered activated carbon, or liquid and solidorganics can be fed into the system either with the wastewater influentvia line 9, or through lines 13 with the sludge return after the sludgeseparator.

Referring now to FIGS. 15 and 16, there is shown a combined openstructure for wastewater treatment, sludge separation andreconditioning. The structure consists of a rectangular tank formed byouter walls 35, and having internal partitions 36 extended for afraction of the total tank height. These partitions 36 form multiplesludge conditioning compartments 4, each compartment having a pyramidbottom 38.

The tank volume above the level of partitions 36 houses the anaerobicreactor 1. A sludge separating means 2 in the form of a settling troughis disposed in the reactor volume. Pipes 9 and 11 are provided forwastewater influent and for treated wastewater respectively. Means 70for mixing sludge is in each sludge conditioning compartment 4, andmeans 71 for mixing the anaerobic mixed liquor is in the reactor area 1.As here shown, the means 70 and 71 are submersible mixers. The structurealso includes means for transferring the conditioned sludge from eachsludge conditioning compartment 4 to the reactor zone 1, for example apump 32 and pipes 13. Pipes 14 are provided for discharging the excesssludge from the sludge conditioning zones. The sludge conditioning inthis apparatus corresponds to the combination of the flow charts shownin FIGS. 2 and 3.

In the operation of this embodiment, wastewater influent is fed into theanaerobic reaction zone by pipeline 9, the sludge is fed in theanaerobic reaction zone 1 by the pump 32 via pipes 213 from a selectedsludge conditioning compartment 4. The liquid in the anaerobic reactionzone is mixed by the gases, generated in the reaction and sludgeconditioning zones, and also by the mixing device 71. The mixturesincluding the wastewater undergo transformations as previouslydescribed. The gases leave the anaerobic reaction zone through the opentop of the apparatus. Appropriate sludge conditioning results in: (a) asufficiently high pH in the reaction zone (near neutral to slightlyalkaline) so that hydrogen sulfide is substantially dissociated intononvolatile ions; (b) a low content of volatile fatty acids and otherodorous compounds in the mixed liquor; and, (c) low hydrogen sulfidegeneration due to the lack of carbon source for sulfate reducingorganisms, so that the gases leaving the anaerobic reactor are composedmainly of nonodorous methane and carbon dioxide.

The mixed liquor is transferred into a sludge separation means 2, suchas a settling trough, a clarifier, a centrifuge, or a filtration device.The clarified water after the sludge separation device 2 is evacuatedfrom the anaerobic system, while the sludge is returned in the anaerobicreaction zone 1 and eventually in the sludge conditioning zones 4. Thesludge in the sludge conditioning zones undergoes transformations aspreviously described. A sludge mixing means is provided in each sludgeconditioning zone. It can be a circulation pump, a propeller mixer(mixer 70 in FIG. 16), or the like. Addition of the necessary reagents,powdered activated carbon, liquid or solid organics, etc. as previouslydescribed, can be provided. The excess sludge can be discharged viapipes 14.

FIG. 17 illustrates a variation of the structure shown in FIG. 16. Thedifference in FIG. 17 is the provision of aeration compartments 130 overthe entire open surface of the open anaerobic structure. These aerationcompartments 13 are formed by an array of vertical baffles 131, with airsupplied to the compartments via main 132, and distribution lines 133.Alternatively, compartments 130 can be formed by inclined submergedbaffles as described in the U.S. Pat. No. 4,472,358, or other packedmedia may be provided.

Thus, the embodiment shown in FIG. 17 is similar to the device of FIG.16, and the operation is similar. The difference in the embodiment ofFIG. 17 is that further elimination of odorous gases is achieved by theuse of the aerated compartments 130 supplied with air via pipe 132 andair distribution branches 133. Aeration causes propagation of theaerobic and facultative organisms which consume residual odorousorganics and oxidize residual hydrogen sulfide.

The mixed liquor is transferred from the anaerobic reaction zone into asludge separation means 2, such as a settling trough, a clarifier, acentrifuge, or a filtration device. After the sludge separation device2, the clarified water is evacuated from the anaerobic system, while thesludge is returned to the anaerobic reaction zone 1, and eventually tothe sludge conditioning zones 4.

The balance of the operation is like the embodiment of FIG. 16, and willnot be repeated.

Apparatuses illustrated in FIGS. 8 to 17 correspond to combined flowcharts such as those shown in FIGS. 1 to 5, and have multiple sludgeseparators. For example, in FIGS. 14, 16, and 17 a sludge separator 2 isused to return sludge through a zero volume channel, such as 5c in FIG.3, and a sludge separation zone at the interphase of the reactor 1 andconditioners 4 is used to return sludge to the plurality of conditioners4 (as in FIG. 2).

A sequencing batch reactor is shown in FIGS. 18 and 19. It consists ofthe outer shell 35 housing the reaction zone which is subdivided intovolumes of influent 400 and dilution (optional) 401; and, the sludgeconditioner consists of a single or multiple chambers 4 formed by thecentral pipe 39 and radial baffles 36. A bladed mixer 490 is supportedby a structure 491, the mixer having a shaft 492 carrying one or moresets of mixer blades 493 and 494. A circulation and mixing pump 32, withpipes 410, 413, and 431, and valves 411, 412, is provided. Pipe 409 forfeeding influent and discharging effluent is connected to the centralpipe 39. An optional dome for gas collection may be provided.

The apparatus is operated as follows: As the cycle begins, the liquidlevel is at the top of the dilution level. Gradually, influent fedthrough pipe 409 fills the influent volume 400. During the filling step,sludge from a single or selected multiple compartments 4 is mixed withwastewater using pump 32, and piping and valving, and also the mixer490. Mixing continues until the wastewater is sufficiently treated,which can be determined by chemical analyses or through measuring gasproduction intensity. After that, all mixing is stopped and sludge isallowed to settle below the influent volume. The influent volume isdecanted via the central pipe 39 and pipe 409. Gas can be discharged tothe air. After that, the cycle is repeated.

The optional diluting volume serves to reduce the occasional highconcentrations of toxic slugs in the influent, thereby avoiding sludgepoisoning and insuring adequate treatment.

The apparatus shown in FIG. 20 differs from that shown in FIGS. 18 and19 by the casing 439 installed around and above the central pipe 39, bythe gas deflecting cone 440 placed under the casing 439, and also by theuse of an injection mixer 418 provided with pipe 415 and valve 414.

The operation of this apparatus is also similar to that described forFIGS. 18 and 19. The provision of the casing 439 and cone 440 helps toavoid drafting of the floating sludge into the effluent as it descendsfrom the upper to the lower position. It also reduces gas mixing effecton the settling sludge because the gas passage in the casing 439 and thecentral pipe 39 are excluded. Optionally, the space between the centralpipe 39 and the casing 439 serves as a suspended sludge blanketclarifier. Accordingly, it separates clarified water from sludgeparticles entering this space through a slot between the cone 440 andthe casing 439. The clarification option requires that the upflowvelocity in the said space is low and limited to the settling velocityof sludge particles in the sludge blanket.

The apparatus shown in FIG. 21 is a further improvement of apparatusshown in FIG. 20 by using additional injection mixers 419 at the top ofthe reactor, provided with pipes 416 and a valve 417. Operation ofinjectors 419 allows for degassing and sinking of the floating andbuoyant sludge. Accordingly, the effluent carries out less suspendedsolids.

The embodiment shown in FIG. 22 is yet another improvement of theapparatus shown in FIGS. 18 and 19. It has a cone 440 around the centralpipe 440 and a cone 441 formed by a plate covering the peripheralsection of compartments 4. Baffles 36 are provided with gas openings451. An upper section of the cone 440 is connected to the cone 441 by agas pipe 442. A gas removal pipe 450 is connected to the upper sectionof cone 441. A slot 460 is formed between cones 440 and 441 allowing thesludge to settle into compartments 4 and excluding gas flow from thesecompartments into the reaction/sludge separation zone.

In the course of operation, a portion of the gas generated in sludgeconditioning compartments 4 is collected under cones 440 and 441, and isevacuated by pipes 442 and 450. At the end of the cycle, sludge isdegassed in the reaction zone by mixers and settles into the sludgecompartments 4. Accordingly, the decanted effluent is better clarified.

FIG. 23 illustrates a sequencing batch reactor similar to that shown inFIGS. 18, 19 and 20, and is provided with a built-in degassing andsettling tank 461. The settling tank 461 is provided with a centraldegassing/water distribution unit comprising a wider section 462 withcirculation cones 466 (see U.S. Pat. No. 4,472,358) and pipe 413, anarrower section 463 with water distribution cones 464 and 465, with acircular trough 467 for collecting clarified water with pipes 468 and469 for effluent discharge and recirculation, with a sludge airlift 470and air pipe 480. The weight of settling tank 461 is supported bystructure 460 on top of the central pipe 39.

The system operates as follows: The influent is gradually added from theminimum water level to the maximum water level. Pump 32 mixes andcirculates the sludge and wastewater from the selected sludgecompartment 4 to the reaction zones 400 and 401 via pipes 413 and 415and injection device 418, and also via settling tank 461. In the widersection 462, due to turbulence and circulation around the cones 466,sludge is degassed. The clarified water from the settling tank isrecycled in the reaction zone through line 469, and separated sludge isreturned to the reaction zone by airlift 470. When a batch of wastewateris adequately treated, line 469 is closed and line 468 is opened todischarge the treated clarified effluent. When the water level drops tothe minimum level, the cycle is repeated.

The embodiment of the invention shown in FIG. 24 includes an anaerobicreactor 1, the output of which is directed by pipe 10 to a sludgeseparator 2. The sludge from the sludge separator 2 passes through thepipe 12 and into the sludge conditioner 3, while the liquid effluentgoes through the pipe 11 and into the aerobic reactor 15. The dischargefrom the aerobic reactor 15 is directed to the sludge separator 16.

The discharge from the sludge separator 16 includes the aerobic sludge,which is moved by the pump 24 through the pipe 44 and into the sludgeconditioner 3. Optionally, this sludge can be directed to reactor 1. Theliquid effluent passes through the pipe 17 from which it may bedischarged to the environment, or at least partially directed to theanaerobic reactor 1 to be recycled.

It should be noticed that reactor 1 is operated in the incompletetreatment mode, and there is a by-pass line 119 to allow the influentfrom the line 21 to be directed immediately to the aerobic reactor inorder to generate a greater quantity of aerobic sludge.

The system shown in FIG. 24 is known under name "coupledanaerobic/aerobic method". The use of the anaerobic stage with sludgeconditioning is a novel feature of the system. Advantages of this stagehave already been discussed. As in all coupled systems, separate sludgesare cultivated in each stage, and there are no interactions betweenthese sludges because they are forcibly (by the use of sludge separationmeans) separated. As in any conventional system, reactor 2 can includefacultative anaerobic, anoxic, aerobic and other functional zones.However, these zones will be operated with a single sludge.

The additional novel feature of the apparatus shown in FIG. 24 is theuse of the fluid flow control box 19. Briefly, the influent from theline 21 enters the box 19, and is discharged through the line 9.Recycled material from the sludge separator 16 enters the box 19 fromthe pipe 18, and excess liquid is discharged through the line 20. Thereis a nearly constant flow from the box 19 through the pipe 9, so theentire system can be maintained with substantially constant flow.

The flow control box 19 is shown in more detail in FIGS. 25-27, and itwill be seen that there is a body including a large compartment 106 anda smaller, side compartment 105. There is a common wall 100 between thecompartments 106 and 105, and the upper edge defines a notch 102 whichacts as a weir. The box 19 also includes an end compartment 107. Thecompartment 107 adjoins the compartment 106, and is separated therefromby a baffle 104. The baffle 104 does not extend all the way to thebottom of the compartments, so fluid flow is allowed between the twocompartments through the passage 109. A side wall of the compartment 107defines an opening 101 which is narrow, but extends down a substantialdistance.

In operation, therefore, the wastewater influent is fed into thecompartment 107 via pipe 21. The wastewater flow rate Q varies fromQ_(min) to Q_(max). A recycle flow, Q_(r) =Q_(max) -Q_(min) =Constant,is fed into the compartment 106 from the line 18. From the compartment106, a portion of the recycle flow is transferred under the baffle 104through the passage 109 and merges with the flow Q of the influent. Thebalance of the flow Q_(r) overflows the broad weir 102 and flows intothe compartment 105, then into the pipe 20. The influent Q and recyclatefrom the line 18 flow through the opening 101. This combined flow may goin line 9 (FIG. 24).

The use of a broad opening as the weir 102 provides nearly constantwater level in the compartments 106 and 107; therefore, a nearlyconstant flow rate is provided across the opening 101. This isadvantageous from the operations standpoint.

A further modification of the anaerobic apparatus, shown as a portion ofthe system in FIG. 24, is the use of the multiple cell anaerobic reactor1 as illustrated in FIG. 28. This reactor comprises multiple sequentialreactors 1a, 1b, 1c, and 1d, having one-way passages 500 for mixture ofwastewater and sludge. The influent distribution piping 9, 9a, 9b, 9c,9d is; connected to at least cell 1a, 1b, 1c, 1d. Lines for feedingreagents 121, 122, 123, for example, nutrients, PAC, neutralizationchemicals, sulfur bearing substances, etc., are connected to cell 1a.Optionally, reagents can be supplied in any or all cells. Line 10connects the last reactor cell 1d with the sludge separator 2. Sludgeconditioner 3 is provided with the feed line 12 and the conditionedsludge line 13 branching into lines 13a, 13b, 13c, and 13d, eachconnected to an individual reactor cell 1a, 1b, 1c, and 1d. Lines 111,112, 113, 114, 115 for feeding various reagents to the sludgeconditioner are also provided.

Apparatus shown in FIG. 28 can be adapted to various modes of operation.For example, it can be operated in the incomplete treatment mode byfeeding wastewater mostly in the inlet cell 1a thus insuring goodacidification, and feeding a deficient flow of methanogen mostly in lastsections (1c, 1d) of the reactor thus reducing contact time formethanogens to consume fatty acids. The reactor 1 can also be optimizedto treat time variable organic loading by distributing unequal fractionsof influent cells 1a, 1b, 1c, 1d and produce equalized effluent. Or, itcan be optimized to minimize the reactor volume by providing distributedfeed of influent and/or conditioned sludge among cells 1a, 1b, 1c, 1d.Alternatively, cells may be used for different functions. For example,the entire influent may be fed into cell 1a with no, or very little,feed of the conditioned sludge into this cell. Then, cell 1a becomes anacidification step. The following cells, 1b, 1c, 1d may be fed with theconditioned sludge to be operated in a methanogenic regime. Accordingly,such a reactor affords flexibility of operation.

FIG. 29 is an example of a reactor with multiple sludge compartments 4and multiple reactor cells 1a and 1b. This structure is similar to FIG.8 and differs only by extending some or all baffles 36 upward usingextensions 536. These extensions go into the gas collection section 33,and divide the total reaction space into multiple cells. One-waypassages 500 are provided in the extension baffles 536. The apparatus isoperated as a sequence of cells in the embodiment shown in FIG. 28.Optionally, sludge conditioning compartments located under a givenreaction cell can be used in conjunction with another (not overlying)reaction cell.

Referring now to that embodiment of the invention shown in FIG. 30,there is an aerobic reactor 202 with the influent conduit 201, and aline 203 for supplying an oxidizer, an optional line 204 for feedingnitrates, nitrites or other source of nitrogen (e.g. urea), a line 205connecting the reactor 202 to an anaerobic reactor 207 (preferably withsludge conditioning zones as in FIGS. 8 or 19), an optional line 206 forfeeding nitrates or nitrites into reactor 207 (or line 205 connected tothe reactor 207), a line 208 connecting reactor 207 to a sludge/waterseparator 209, lines 210 and 21 Connected to the separator 209 for theevacuation of sludge and water respectively, and a line 212 with a pump213 connecting the sludge pipe 210 to the bioheating reactor 202.

In operation, the sludge is fed via line 201 in the aerobic reactor 202.The oxidizer (air, or oxygen enriched air, or oxygen) is also fed intoreactor 202. Optionally, nitrates, nitrites or other source of nitrogenare also added to or generated in the reactor 202. In the reactor 202,organics of the sludge are oxidized and heat is generated. Accordingly,sludge temperature increases and viscosity of the liquid phasedecreases, providing improved conditions for sludge/water separation.Most of the nitrogen forms in the liquid phase are converted intonitrites and nitrates. From reactor 202, sludge is transferred into theanaerobic reactor 207 via line 205. Optionally, nitrates and/or nitritesare added to the sludge in the line 205 or in the reactor 207. Inreactor 207, aerobic sludge is converted into anaerobic sludge and atleast partially digested. Digestion is enhanced and accelerated due tothe elevated temperature of the sludge fed into the reactor 207. Duringdigestion, carbon dioxide, methane, and nitrogen are produced in theform of small bubbles. The digesting sludge is transferred via line 208to the flotation type sludge/water separator 209 wherein the bulk ofsludge floats up and is evacuated through the pipe 210; the water isevacuated via pipe 211. Optionally, a portion of the floated sludge isrecycled to the reactor 202 via line 212 with the use of conveying means(a pump) 213. The organic fraction of the recycled sludge isadditionally oxidized in the aerobic process in reactor 202 thusproviding higher temperature of the sludge in the reactor 202 andfurther down the flow. The anaerobic process rate and the sludge/waterseparation are accelerated at higher temperature.

FIG. 31 shows another system for sludge thickening comprising a feedpipe 201 connected to an aerobic bioheating reactor 202. Reactor 202 isprovided with line 203 for oxidizer supply and optional means 204 forfeeding nitrates, nitrites or other sources of nitrogen. A branch 214 isconnected to pipe 201 and leads to an anaerobic reactor 215 installed inparallel to reactor 202. The aerobic reactor 202 and anaerobic reactor215 are connected to the anaerobic reactor 207 by pipes 205 and 216. Thereactor 207 (preferably, with sludge conditioning zones) is optionallyprovided with a line 206 for feeding nitrates and/or nitrites. Reactor207 is connected by means of pipe 208 to the sludge/water separator 209.Pipes 210 and 212 are provided in the separator 209 for evacuation ofthe floated sludge and water respectively. A branch 212 with a pump 213is provided for recycling of a portion of the sludge to the aerobicreactor.

In addition to the process steps previously described, an anaerobiccultivation step, carried out in reactor 215, is employed in thissystem. In this step, anaerobic organisms are cultivated so that, whenheated, aerobic and anaerobic sludges are mixed, the anaerobic processin the reactor 207 is accelerated by the inoculum from the reactor 215,and the volume of this reactor is reduced. A portion of the recycledfloated sludge can be optionally fed in the anaerobic cultivation step,reactor 215. This will increase temperature in the cultivation step andaccelerate the process rate.

FIG. 32 illustrates a system for sludge thickening and drying. Thesystem comprises an aerobic bioheating reactor 202 having anaerobicsludge conditioning compartments 4 with sludge circulation means (notshown) at the bottom, sludge feed pipe 201, and oxidizer via line 203and aerators 217. Reactor 202 is connected to a sludge bed 219 by a pipe205 with a valve 218. The sludge bed 219 may have a concrete bottom 220with one or several drainage channels 221 housing perforated drainagepipes 222. Pipes 222 are surrounded by a gravel layer 223 overlaid witha sand layer 224.

Operation of the system shown in FIG. 32 is as follows. sludge isperiodically fed via pipe 201 into the reactor 202 and aerated by air(or oxygen enriched air, or by oxygen). During aeration, sludge becomesheated. A fraction of the sludge is anaerobically conditioned incompartments 4. A portion of the heated sludge is periodically addedwith some anaerobic sludge from compartments 4 and is transferred viapipe 205 by opening valve 218 onto the sludge bed 219. On the bed 219,aerobic sludge inoculated with added anaerobic sludge rapidly turnsanaerobic, gases are generated, and the sludge particles are floated bythese gases to the top of the sludge charge leaving the bottom layer ascomparatively clear water. Clear water flows laterally to the channel221, filters through the sand 224 and gravel 223 layers in the drainagepipe 222, and is evacuated from the system via drainage pipe 222. Thefloated sludge layer subsides and remains on the concrete floor 220until dry. Dry sludge is removed from the bed manually or mechanically.A thin layer of sand over the channel 221 may also be removed. This sandshould be replaced periodically with fresh sand. Optionally, the entirebed may be made of sand layer.

Due to the use of the conditioned anaerobic sludge with massive supplyof methanogens, fatty acids are rapidly consumed and sulfides are notgenerated. Moreover, complete treatment of filtrate occurs and itsrecycle back to the water treatment train does not increase the organicloading on the treatment processes.

FIG. 33 illustrates another modification of the system for sludgethickening. This modification comprises an aerobic bioheating reactor202 with line 201 for feeding the raw sludge, a line 203 and aerators217 for feeding oxidizer (air, oxygen enriched air, or oxygen) and line205 for transferring the bioheated sludge to the anaerobic reactor 207.Reactor 207 is equipped with a mixing means 225. This reactor isconnected to the sludge/water separator 209 via pipe 208. Separator 209is provided with pipes 210, 211, and 226 for removal of the floatedsludge, clear water, and heavy sediments respectively. An optionalsludge recycle pipe 212 with a pump 213 connects the line 210 with thereactor 207.

The system illustrated in FIG. 33 is operated in a continuous regime.Raw sludge is fed via pipe 201 into the reactor 202, oxygen for aerationis supplied through the line 203 and aerators 217. Organic matter of theraw sludge is consumed and oxidized by bacteria, and the sludge isbioheated. The heated sludge is transferred via pipe 205 into theanaerobic reactor 207, wherein the contents are mixed by means 225. Atleast partial digestion of the sludge occurs in the reactor 207 anddigestion gases are generated. After that, the sludge is conveyed to thesludge/water separator 209 via pipe 208. In the separator 209, gasesfloat up the sludge particles and an underlying layer of comparativelyclear water is formed. A small quantity of heavy particles settles downin the separator 209. Floated sludge is evacuated via pipe 210 anddirected to a further treatment, for example, to a rotary dryer. Aportion of the floated sludge is optionally recycled for inoculation tothe reactor 207 via pipe 212 by a pump 213. Clear water is dischargedthrough the pipe 211, and heavy sediments are removed through the pipe226.

FIG. 34 illustrates a system for periodic (batch) treatment of sludge.The system comprises an aerobic reactor 202 for sludge bioheating and areactor/separator 207, 209) for anaerobic digestion and sludgeflotation. Reactor 202 is provided with a pipe 201 for feeding rawsludge, and a pipe 205 for transferring the bioheated sludge fromreactor 202 to reactor 207, 209. An oxidizer line 203 and aerators 217are provided in the reactor 202, while a mixer 225 is installed in thereactor 207, 209. Reactor 207, 209 is also provided with pipes 210, 211,and 226 for the evacuation of the floated sludge, discharge of theclarified water, and discharge of the heavier sediments.

The system illustrated in FIG. 34 is operated as follows. Raw sludge isfed into the reactor 202 by the pipe 201 until the maximum level isreached. During this fill time, the sludge is aerated with air, oroxygen, or oxygen enriched air, and becomes bioheated. A portion of theheated sludge equal to the volume of the reactor 207, 209 is transferredby the pipe 205 to the anaerobic reactor 207, 209. In this reactor, thesludge is at least partially digested and the anaerobic gases aregenerated. Mixing may be provided during the digestion period. After thedigestion period, mixing is stopped and the sludge flotation is allowedto proceed. At the end of the flotation period, the bulk of the sludge,clarified water, and heavier sediments are removed from the reactor 207,209. A portion of the sludge is left for inoculation of the next batch.By this time reactor 202 may already be filled again. Then, a portion ofthe heated aerobic sludge is transferred to the reactor 207, 209 and thecycle is repeated.

FIG. 35 illustrates a layout of the improved anaerobic-aerobic system.The system comprises the anaerobic reaction stage 1 disposed abovemultiple sludge conditioning sections, or compartments, 4a, 4b, etc.There is a combined upflow reaction-sludge-separation stage 600 having acentral downcoming pipe 601 and collection trough 602, and a reactionstage 301 with a sludge separator 300.

The anaerobic reaction stage and sludge conditioning sections areequipped with a sludge separation device 2, such as a lamella clarifier.The clarifier has outlets 11a and 11b connected to stages 600 and 15respectively, a mixing means 71, influent feed pipe 9 with branches 609and 119, and line 13 with branch 613 for sludge recycle from the sludgeconditioners to the anaerobic reaction stages 1 and 600 by means of apump 32, and a line 14 for sludge discharge.

The combined reaction-sludge-separation stage consists of a downflowpipe 601 and an upflow section 600. A water collection trough 602 isinstalled at the top of the section 600. This trough is discharged intoaerobic section via line 603. Section 600 is preferably an upflowsuspended sludge blanket reactor. Optionally, section 600 may be filledwith a fluidizable medium, such as sand, granular activated carbon,crushed porous baked clay (ceramsite) or other suitable medium. Thesuspended sludge blanket and fluidizable media are preferred in caseswhen a risk of plugging the fixed medium exists. Adsorption media, suchas carbon, or attached biomass, constitute an active material in thebed. Also optionally, packed bed of stone or fixed plastic media canalso be used.

The reaction stage 15 is equipped with air pipes 480, aerators 217, andan airlift means 470 for transferring mixed liquor from the reactorstage 15 via lines 610 and 611 to sections 1 and 600. Means (not shownin figures) are provided for the optional feeding of the powderedactivated carbon (PAC), coagulants and other reagents listed in theprevious discussions. Optionally, stage 15 may be a submerged biologicalfilter, a GAC upflow reactor, or other reactor type or a combination ofreactors.

Motorized and manual valves are provided on air, wastewater and sludgelines.

The system is operated as follows. Wastewater is fed into the anaerobicreaction stage 1 and is mixed by the mixing device 71 with the anaerobicsludge grown in this stage and conditioned in the sludge conditioner 40.Some conditioned sludge is recycled via line 13 by a pump 32. The excessconditioned sludge is discharged via line 14. Mixed liquor is partiallyclarified in the sludge separator 2 with the sludge falling back intothe reactor stage 1, and a fraction of incompletely treated clarifiedwater being discharged via pipe 601 to the reaction stage 600. Thebalance of the clarified water is transferred to the reaction stage 15via line 118. Biological and other processes in the anaerobic functionalzone are the same as previously described. Additionally, a small flow ofthe anaerobic conditioned sludge may be directed via line 613 to pipe601 and reactor 600. Organics in the incompletely treated clarifiedwastewater and the mixed liquor after the anaerobic stage arerepresented mostly by easily degradable fatty acids and other simplecompounds. Only a small proportion of the constituents in this streamare residuals of poorly degradable and toxic and recalcitrant organics.

The clarified water and conditioned sludge from the anaerobic stage 1and conditioners 4, and the mixed liquor from the aerobic stage 15, arefed to the downflow pipe 601 of the reaction stage 600. In part, GAC isregenerated by desorption of certain constituents and readsorbtions ofthem by the PAC flowing through and removing these constituents from thereactor and eventually (with wasted sludge) from the system. Optionally,a portion of the wastewater influent is also fed into section 600 vialine 609 and pipe 601. The flow from the stage 15 via airlift 470 andpipe 611 may carry substantial quantities of nitrates and nitrites. Fromthe downflow pipe 601, the mixture of waters and aerobic and anaerobicsludges is directed into the upflow section 600. For the purposes ofdiscussion, it is assumed that the section is filled with a fluidizedGAC, which is the first active material; operation of this section withother fluidizable material or with a fixed bed is very similar. The GAClayer is fluidized by the upflow. GAC is retained in the section 600,while the lighter biological sludge, with or without PAC, is passingthrough the section 600 and is fed into the reaction stage 15 via pipe603. PAC and associated biomass, or their combination, constitutes asecond active material in the reaction zone. The combined sludge in thesection 600 is composed of aerobic and anaerobic organisms. The biomassattached to the GAC particles is predominantly anaerobic, while thatattached to the PAC particles coming from section 15 is aerobic.Therefore, enzymes originated in aerobic and anaerobic environmentssimultaneously act upon and degrade organics, including residualquantities of recalcitrant and toxic compounds. Moreover, nitrates andnitrites are reduced by denitrifying organisms to nitrogen and water.Some nitrites and nitrates will be reacting with poorly degradable,recalcitrant and toxic organics. Optionally, nitrates and nitrites maybe added in the section 600 to increase the effect of oxidation of suchorganics. Chemical reaction between ammonia and ammonium ions, andsulfide and sulfide ions on one hand and nitrites and nitrates andsulfites and sulfates result in formation of nitrogen and sulfur.

The stage 600 described in this embodiment is a novelreaction-separation method and device in which part of the sludge isretained (grown and immobilized) on the GAC, and another portion ispassed through with the PAC (or in form of biological flock found inusual sludge). Optionally, the fluidized bed may be formed by a granularanaerobic sludge grown with PAC. The adsorption capacity of either GAC,or granular sludge with PAC is regenerated biologically using activeagents associated with aerobic and anaerobic sludges simultaneouslypresent in the system. Optionally, multiple parallel stages 600 operatedsimultaneously, or in a queue may be used.

Aerobic biochemical processes occur in the reaction stage 15, possiblywith the nitrification. The nitrogen control in the effluent is providedby chemically reacting ammonia and nitrites and nitrates and biologicalreduction of nitrates and nitrites in the reaction-separation stage 600.Ammonia is generated in anaerobic stages 1 and 600. Reaction betweennitrogen oxides and ammonia and/or sulfides reduce the total ammonia toa greater extent than denitrification alone, so that the nitrogenleaving the section 600 is just what is needed for aerobic organisms instage 15. Therefore, a thorough nitrogen removal is provided. Phosphoruscontrol is provided by partial biological uptake and by addition ofreagents, such as iron and aluminum coagulants, or others, preferably tothe reaction stage 15.

Referring now to FIGS. 36 and 37, there is shown an alternativeapparatus for practicing the method of this invention. The apparatusconsists of an anaerobic reaction stage 1 made of several compartments1a, 1b, etc., an anaerobic sludge conditioner 3 located centrallyrelative the said anaerobic compartment 1, an aerobic reaction stage 15disposed above the anaerobic compartment 1 and the sludge conditioner 3,and a sludge separator 16 located in the upper section of the aerobicreaction stage 15.

The anaerobic compartments 1a, 1b, 1c, etc. can be a free volume sectionwith a fluidized blanket of anaerobic sludge or, optionally, be loadedwith fluidizable coarse bed media such as sand, granular activatedcarbon, or crushed packed porous clay (ceramsite) or they may have afixed bed of stone or plastic contact medium or other packing type.Granular anaerobic sludge with or without PAC can also be used as afluidizable material. The aerobic reaction zone 15 can optionally bepacked with a support material providing the attached growth as insubmerged biofilters. The aerobic stage is equipped with aerators 217.Feed line 24 for the influent is connected to a constant flow box 19,this line continues downward as line 9 and is connected to a ring pipe1R having branches 1a, 1b, 1c, etc. with valves for each anaerobiccompartment 1a, 1b, 1c, etc. A line 48 with a pump 47 connects aerobicstage 15 to the anaerobic compartments 1 via lines 9, 9R and branches9a, 9b, 9c, etc. Line 13 and pump 32 connect the bottom part of thesludge conditioner via the ring pipe 9R and branches 9a, 9b, 9c, etc. tothe bottom part of the anaerobic compartments 1a, 1b, 1c, etc. Pipe 14is the sludge discharge. Pipe 617 connects the volume of the aerobicstage 15 to the separator 16, which is shown here as a vertical flowclarifier. An airlift 470 is installed in the clarifier 16 fortransferring the separated sludge to the aerobic reaction stage 15. Pipe18 further connected to pipe 17 is provided at the clarifier 16 of theeffluent discharge. The effluent recycle pipe 18 with a pump 23 connectsthe effluent pipe 18 to the constant flow box 19. An overflow pipe 20connects the box 19 to the effluent line 17. Means for feeding variousreagents (not shown) as previously described are also provided. Thesemeans may be attached to feed said reagents to either aerobic reactionstage 15 or anaerobic compartments 1.

The system is operated as follows. The wastewater influent and therecycled effluent are fed via lines 24 and 20 into the constant flow box19. The constant flow of the influent and recycled effluent mixtureproduced by the box 19 is fed via lines 9, 9R, and 9a, 9b, 9c, etc. intothe selected compartments 1a, 1b, 1c, etc. A recycled flow of the mixedliquor from the aerobic reaction compartment 15 is fed into theanaerobic compartments 1a, 1b, 1c, etc. by the pump 47 via line 48. Oneor several compartments can be selected by opening or closing valves onbranches 9a, 9b, 9c, etc. The upflow streams fed into the selectedanaerobic compartments fluidize the bed of biological sludge, or the bedof the coarse material supporting the sludge (sand, GAC, ceramsite). Theoriginal organic materials and metabolic products from the aerobicreaction stage 15, including nitrates and nitrites, are anaerobicallyconverted in the compartments 1 forming anaerobic biomass, methane,carbon dioxide, hydrogen, sulfides, nitrogen, and residual fatty acidsand other organics, including residual poorly degradable and toxicconstituents. If GAC is packed in compartments 1 and PAC is added to themixed liquor, preferably in the aerobic reaction stage 15, the processesoccur in the manner as described above. This anaerobic stage convertsorganics and inorganics, including nitrogen removal. Recycle via line 48provides a repeated (alternating) anaerobic-aerobic treatment oforganics and metabolic products. The suspended solids and some organicsare coagulated and flocculated by both the aerobic sludge brought in viarecycle pipe 48, and the conditioned anaerobic sludge fed via lines 13and 9a, 9b, 9c, etc. and the anaerobic sludge cultivated in thecompartments 1. The process can further be improved by applyingpreviously described physical, physical-chemical and chemical actions tothe anaerobic system in compartments 1.

The mixed liquor leaving the selected compartments 1 enters an areabelow the aerators 217 and above the top of compartments 1. Here, partof the sludge settles down by gravity into the sludge conditioner 3, andonto the top of compartments 1 that are not selected at the time.Anaerobic sludge is conditioned in the sludge conditioner as previouslydescribed. Part of this sludge is recycled to the anaerobic reactioncompartments 1, and the balance is discharged through the line 14. Theliquid flow from the selected anaerobic compartments 1 with residualorganics and with the residual suspended solids enters the aerobicreaction stage, is subjected to the aerobic treatment with correspondingorganics removal, suspended solids coagulation-flocculation by thesludge, nitrification, and partial phosphorus removal due to themicrobial uptake. Coagulants and flocculants; can be added to improvethe sludge settling and for removal of phosphorus. PAC and otherreagents can also be used with the benefits previously described. If theoptional support medium is provided, an attached growth of aerobicbiomass will occur. It will improve nitrification-denitrification in theaerobic reaction stage 15. The anaerobic gases will cross the aerobicreaction stage 15 and become additionally treated. Thus, residualhydrogen sulfide will be partially oxidized to sulfite and sulfate, andpartially converted to sulfur. Ammonia will react with nitrites andnitrates to become nitrogen. Organic gases will be mostly absorbed andaerobically metabolized. Methane will be partially absorbed, metabolizedby methanotrophic bacteria and support the growth of such bacteria. Thisis very useful for co-metabolizing the chlorinated organics. The aerobicmixed liquor is fed into the clarifier 16 through pipe 17, precipitatedto the bottom of the clarifier, and recycled back to the aerobicreaction stage via airlift. The clarified water is evacuated at the topof the clarifier via line 17. Part of the clarified water is dischargedby line 17 and the balance is fed by pump 23 via line 18 to the constantflow box 19. The excess recycle flow is discharged by line 20 to theeffluent discharge line 17. The aerobic sludge is partially circulatingin the aerobic reaction stage 15, and partially is pumped through theanaerobic compartments 1 by line 48 and pump 47, and partiallyprecipitates to the anaerobic sludge conditioner 3. Regardless of thepathway, all aerobic sludge is eventually transferred to the previous,anaerobic stage. Optionally, section 15 may be separated into multiplecompartments operated as facultative, anoxic, aerobic, and polishingprocess steps.

Modifications to the system presented by FIGS. 36 and 37 may includemultiple sludge conditioning zones, a single upflow reaction zone, theuse of a downflow fixed bed reaction zone instead of the upflow reactionzone, additional polishing zone, for example, a chemical-biologicaltreatment in a biofilter with the addition of PAC and coagulants for thepurposes previously described.

The system depicted in FIGS. 36 and 37 can also be used as a sequencingbatch reactor with anaerobic-aerobic cycles. In batch mode, the sludgeseparation means 16 is not required, and an alternative discharge line17a for the effluent is provided.

The batch system is operated as follows: At the beginning of the cycle,the liquid level in the reactor is at the level of pipe 17a. Gradually,the reactor is filled and the liquid is pumped by pump 47 throughselected compartments 1, thus undergoing initial anaerobic treatment.Aerobic sludge originally placed on the top of the anaerobic sections 1is also involved in the anaerobic cycle. Later, the filling continuesand aeration starts. Now, partially treated aerobically, wastewater-isrecycled through compartments 1. This constitutes alternatinganaerobic-aerobic treatment. After complete filling and additionalaeration and anaerobic-aerobic recycle, the treated wastewater isallowed to separate from the settling sludge. Separated water isdecanted. The aerobic sludge remains on top of anaerobic compartments. Aportion of anaerobic and aerobic sludges is conditioned in sludgeconditioner 3. Conditioned sludge is recycled and periodicallydischarged from the system. Optionally, a portion of the reactioncompartments 1 may be aerobic. In such a case, aeration means can beprovided in these sections.

The system given in FIGS. 36 and 37, either flow-through or batching,can also be used for sludge digestion.

Systems shown in FIGS. 35, 36 and 37 are examples of a new generic typewhich can be called combined anaerobic/aerobic system. It combines theproperties of the coupled anaerobic/aerobic system (distinct sludges,anaerobic upstream, aerobic downstream; highest sludge concentration inthe front section where the waste concentration is the greatest) and theproperties of the ASP with facultative anaerobic, anoxic, and aerobiczones but with a single sludge. This combination is achieved byrecycling all sludge transferred from upstream sections and grown in thedownstream sections (sections 15 in FIGS. 35 to 37) back to the upstreamsections (1 in FIGS. 36, 37 and 600 and 1 in FIG. 35), transferring aportion of the sludge from upstream to downstream sections (in FIG. 35pumping some sludge from conditioners 4 via line 613 to the section 600,and transferring sludge from section 600 down to section 15; in FIGS. 36and 37, some anaerobic sludge carried up by the flow in compartments 1is admixed with the sludge in aerobic compartment 15). Accordingly,there is a smaller downflow and a greater upflow of sludges in the new(combined) system, with the resultant counterflow of water (down) andsludge (up) and the excess sludge wastage at the upstream. In such asystem, both the water with admixtures in it, and the sludges areexposed to the widest range of environmental conditions, enzymes, ORP,etc., and can be better converted and degraded, while discharged sludgeis stabilized.

Referring now to FIG. 38, there is shown a system for treatment of gasesbearing biodegradable constituents, the biodegradable constituents beingin gaseous or particulate form, or both. The system consists of twobiological reaction stages: anaerobic stage 735 and aerobic stage 736.Each stage can be made as a biofiltration section, or a packed scrubber.Sludge separators 2 and 16 may be associated with each reaction stage.Gravity separators disposed under the reaction stages are shown in FIG.38; however, other known separation means as listed above can also beused. A bottom section of the apparatus may be assigned for an optionalsludge conditioner 4. As shown in FIG. 38, the entire apparatus, withthe exception of auxiliary elements, is assembled in a single column737, but other arrangements can also be used. The sludge separator 16 isformed by a tray 793, the wall of the column 737, and the wall of thepassage 722. The sludge separator 2 is formed by the wall of the column737, a tray 794 with a pipe 771 for passing gases upstream, and apassage 710 for the mixed liquor. A gas influent line 9g is connected tothe bottom section of the reaction stage 1. Line 721 with a pump 791connects the sludge separator 16 to the top of the reaction stage 736. Ameans 732, for example a spraying device, is attached to the end of pipe721 at the top of the reactor stage 736. Lines 711 and 13 with a pump32a connect a sludge separator 2 to the top of the reaction stage 735. Aliquid distribution means 717, for example spraying heads, is attachedto the end of pipe 13 at the top of the reaction stage 735. Line 13connects the sludge conditioner 4 to the spraying device 717. A branch713 connects the pipe 13 to, the sludge separator 16. Line 14 for sludgedischarge is attached to line 13. Line 753 for water discharge isconnected to the sludge separator 2 at its top. A pipe 754 is attachedto pipe 721 to feed fresh water and reagents, for example, PAC,coagulant salts, supplementary organics, etc. A line 755 foroxygen-containing gas (air, or oxygen, or both) is connected to thebottom of the reaction stage 736. Pipe 737g for discharging the treatedgas is attached to the top of the reaction stage 736.

This system is operated as follows: The polluted gas is fed at thebottom of the reaction stage 1 via line 9g and flows upward across thepacking. Conditioned anaerobic sludge from the sludge conditioner 4 anda clarified, or partially clarified, anaerobic supernatant from the topof the sludge separator 2 are fed by pumps 32 and 32a via line 13 to thetop of the reaction stage 1 and sprayed over the reactor packing by aspraying device 717. The sprayed mixture of anaerobic sludge andsupernatant come into contact with the gas fed into the reaction stage101 and scrub and absorb a fraction of the pollutants from the gas.Biological growth in the reaction stage 1 occurs on the packing(attached growth) and in the suspension. If PAC is fed into the system,biological growth occurs also on suspended PAC particles. Hydrolyzing,acidogenic and methanogenic microorganisms are grown in the reactorstage 1. Other specialized groups of organisms may also be present,particularly sulfate reducers. Organic particulates scrubbed in thisreactor are at least partially solubilized by the hydrolyzing organisms,soluble materials are at least partially converted into fatty acids andcarbon dioxide, methane, hydrogen, ammonia, and hydrogen sulfide by theacidogenic and other organisms, and fatty acids are at least partiallyconverted into methane and carbon dioxide by the methanogens.

After passing across the packing in the reaction stage 1, the mixedliquor is collected on the tray 794 and flows via pipe 710 into thesludge separator 2. The clarified water in the separator is collected atthe top and is partially recycled by pump 32a via lines 13 and 713 tothe top of the reaction stage 735, and to the reaction stage 736. Thefraction of the clarified water is periodically or continuouslydischarged via line 735. Make-up water and the above listed reagents areadded to the system through the line 754. The settled sludge goes to thesludge conditioner 14 by gravity, where the scrubbed particulates andincompletely digested soluble organics are additionally digested andconverted to the final products of anaerobic processes. The gasesgenerated in the sludge conditioner 4 pass through the sludge separator2, become collected under the tray 794 and are released to the reactionstage 1 via pipe 771.

The conditioned sludge is recycled by pump 32 through lines 13 and 713to the top of the reaction stage and to sludge separator 16. A portionof the conditioned sludge is discharged continuously or periodicallythrough line 14. After the first stage treatment, the feed gas istransferred through opening 722 to the reaction stage 15 (secondtreatment stage). At the bottom of this stage, the feed gas is mixedwith oxygen-containing gas fed via line 755. The gas mixture flowsupward across the packing in the reaction stage 15 and contacts thedownflowing aerobic mixed liquor. This mixed liquor is recycled by thepump 791 via lines 721, and distributed over the packing means 732.

Attached and suspended aerobic microorganisms are growing in thereactions stage 15. Residual organics, volatile metabolic products fromthe previous stage, and ammonia and hydrogen sulfide are additionallyabsorbed, and removed from the gas by the biomass and water. The bulk ofthe biodegradable materials are oxidized to carbon dioxide and water,ammonia is partially converted to nitrates and nitrites, sulfides arepartially oxidized to sulfites and sulfates. Nitrogen and sulfur arepartially formed through the chemical reactions between ammonia,sulfides, and nitrates and nitrites, and sulfites and sulfates. Nitrogenleaves the system with the treated gas via pipe 737g, and sulfur iseventually discharged with the anaerobic sludge. Some mixed liquoroverflows through the opening 722 to the reaction stage 1. Thisconstitutes a counterflow of the sludge in the overall system. Moreover,nitrates and nitrites carried down to the reaction stage 1 are used upfor oxidation of organics in this stage.

Additional reagents may be placed into the system. Addition of PACresults in adsorption of pollutants from the gas, thus increasing theprocess rate and efficiency. The PAC will take part in the sludgecounterflow and will be used in aerobic and anaerobic reaction steps aspreviously described. Other reagents can also be used as previouslydescribed for the wastewater treatment applications. A specific reagent,source of carbon, or organics, may be needed in the gas treatmentsystems to improve the process stability at highly variable, andperiodic gas loading conditions, or for gases carrying poorly degradableorganics. Preferably, nonvolatile organics should be used. Wastewatermay also be used as a source of organics.

Referring now to FIG. 39, there is shown a basic system of combinedwastewater treatment and transportation. The system comprises thebranched network 700 of wastewater collection and transportation pipesand channels 701, and an end-of-pipe treatment plant 702 having unitsfor anaerobic treatment of wastewater or anaerobic sludge conditioning704, a pumping means 32 and pressure lines 13 for transporting theanaerobic sludge rich in methanogens. The sludge lines 13 are connectedto the sewer lines at points A. A treated wastewater outfall 17 isprovided at the treatment plant. Detailed structure of the treatmentplant is not provided because this information is readily available tothose skilled in the art.

The system of FIG. 39 is operated as follows. Wastewater is collectedfrom the waste generators (houses, commercial and industrialestablishments) into pipes 701 and is transported by these lines to thetreatment plant 702. The methanogens rich sludge is conveyed from theanaerobic treatment or conditioning units 704 by the pumping means 32via pressure lines 13 and is fed into sewer lines at points A. From thispoint on, the wastewater-sludge mixture is carried in the pipes 701downstream.

From the uppermost points in the wastewater network to points A,acidogenic processes are not well developed and just start setting on.Growth of sulfate reducing organisms is also insignificant because theyhave no good carbon source (fatty acids). Accordingly, methanogenicsludge should not be carried an extra distance to the uppermost point inthe network, but preferably should be fed at points A where anaerobicprocesses become significant. From the points A to the treatment plant,parallel acidogenic and methanogenic processes occur. Feedingmethanogens at points A provides rapid conversion and consumption of thefatty acids generated by the acidogens. Accordingly, the sulfatereducers have no food to promote growth. During such biochemicaltransformations, wastewater becomes at least partially treated, thegases produced have virtually no odorous constituents, and corrosivesulfuric acid is not generated in the pipes.

Optionally, provisions can be made for collecting methane gas generatedin the wastewater networks. For example, the manholes on the pipelines701 can be sealed and gas can be collected from the manholes. This gascan be used for driving gas engines, as a heating fuel, or for otherknown uses.

As an alternative, trucking of the anaerobic methanogens rich sludgefrom the unit 704 to points A can be used. The essence and organizationof the biological processes in this system modification is the same ashas been described elsewhere throughout this application.

Referring now to FIG. 40, there is shown another modification of thenovel process. The system comprises the branched network 700 ofwastewater collection and transportation pipes and channels 701, and anend-of-pipe treatment plant 702. Units for anaerobic treatment ofwastewater and sludge conditioning 704 are installed on the pipenetworks at points A. A treatment plant 702 is provided at theend-of-pipe. A treated wastewater outfall 17 is provided at thetreatment plant.

The system of FIG. 40 is operated as follows. Wastewater is collectedfrom the waste generators (houses, commercial and industrialestablishments) into pipes and is transported by these lines to thetreatment plant 702. A portion of all wastewater is intercepted fromthese lines and directed to anaerobic treatment units 704, wherein themethanogens rich sludge is generated as previously described. Thustreated wastewater and excess anaerobic sludge are discharged in thepipes 701. From this point on, the wastewater-sludge mixture is carriedin the pipes 701 downstream.

From the uppermost points in the wastewater network to points A,acidogenic processes are not well developed and just are setting on.Growth of sulfate reducing organisms is also insignificant because theyhave no good carbon source (fatty acids) and the retention time isshort. Accordingly, anaerobic treatment and generation of methanogenicsludge need not be carried in the upper reaches of the pipes network.Moreover, there may be not enough wastewater to generate sufficient massof excess sludge at the upper reaches of the pipes 2. From the points Ato the treatment plant, parallel acidogenic and methanogenic processesoccur. Feeding methanogens at points A provides rapid conversion andconsumption of the fatty acids generated by the acidogens. With suchbiochemical transformations, wastewater becomes at least partiallytreated, the gases produced have virtually no odorous constituents, andcorrosive sulfuric acid is not generated in the pipes. These gases canbe captured from units 704.

Referring now to FIG. 41, there is shown another modification of thenovel process. The system comprises the branched network 700 ofwastewater collection and transportation pipes and channels 701, and anend-of-pipe treatment plant 702. Units for anaerobic treatment of solidor liquid waste 704 are installed at the pipe network by points A. Atreated wastewater outfall 17 is provided at the treatment plant.

The system of FIG. 41 is operated as follows. Wastewater is collectedfrom the waste generators (houses, commercial and industrialestablishments) into pipes and is transported by these lines to thetreatment plant 702. A stream of solid and/or liquid waste is fed intothe anaerobic treatment units 704, wherein the methanogens rich sludgeis generated. If needed, water for the units 704 may be provided fromthe sewerage pipes. Thus treated solid and/or liquid waste is mainlyconverted into anaerobic sludge rich in methanogens. This sludge isdischarged in the pipes 1. From this point on, the wastewater-sludgemixture is carried in the pipes 1 downstream. The rest of the process isthe same as previously described.

Units 704 in either process modification may be a conventional anaerobicsludge digestor, or any of the known anaerobic reactors for treatment ofwastewater, or an organic stock for gas generation. Preferably, theseunits shall be anaerobic treatment apparatuses with sludge conditionersas described in the present application. These apparatuses may beprovided with means for gas collection and utilization. Combinedanaerobic-aerobic apparatuses can also be used.

Multiple units 704 for anaerobic treatment and generation of methanogenrich sludge may be used on all or selected branches of the pipenetworks. The number, location and capacity of these units must bedetermined by balancing the available organic material for the sludgegeneration and the need in the methanogenic sludge downstream from theseunits. In case of pumping methanogenic sludge from the treatment plantas illustrated in FIG. 39, multiple points A may be established on allor selected pipeline branches. Units 704 can double for pump stationsand flow equalization basins. In the latter case, the capacity of thewhole waste management system can be increased.

Referring now to FIG. 42, there is shown an improvement to a wastewatertreatment plant intended for odor control at the front end of the plant.The improvement comprises an anaerobic unit 35 as the first unit at theplant, this unit having an influent line 9 for raw waste. Optionally, acomminutor type on-line means can precede the anaerobic unit. Unit 35 isconnected by line 19a to a screen 900, possibly housed in a building901, and further by a line 101 to a sludge separator 2 (in cases ofupgrading, primary clarifiers can be used for sludge separators).Anaerobically treated water is evacuated via line 11. The sludge ispumped from the sludge separator to the unit 35 by a pump 25a via line12. The unit 35 is similar to that shown in FIG. 8. It has gas line 910,a compressor 911 and lines 912 extending to the pyramidal bottoms forsludge lifting and mixing. Optionally, unit 35 may be open andalternative means can be used for sludge mixing and lifting. Line 14 andpump 25b are provided for discharging excess stabilized sludge from thesystem.

The operation of the system shown in FIG. 42 is the same as previouslydescribed with the exception of screening that is performed not beforebut after unit 35, wherein odorous constituents are eliminated fromwastewater in treatment processes in unit 35.

The system shown in FIG. 42 can be added with a conventional activatedsludge process, or other systems. In many cases, addition of an aeratedgranular bed filter with or without reagents may be sufficient for thefinal treatment. Referring now to FIG. 43, there is shown an automaticcontrol system using the embodiment depicted in FIG. 8 as an example. Inaddition to the elements shown in FIG. 8, there are shown motorizedvalves 820a and 820b (one valve is energized to open, another isenergized to close), a sensing device (probe) 800, preferably a pHmeter, or analyzer for fatty acids, or a combination of both, a line 804for transmitting input signals from the probe 800 to a controller 830,for example, a programmable logic controller or any analog or digitaldevice, and output signal lines 811 and 812 from the controller 830 tothe actuation means 820a and 820b, motorized valves, and/or conveyingmeans for conditioned sludge 32, such as pumps.

The control system in FIG. 43 is operated as follows. A variable flow ofwastewater (or sludge) with variable concentrations and composition ofadmixtures enters the reaction zone 1. Due to this variability, the rateof acidogenic conversion changes (increases when the organic loadingincreases). Accordingly, fatty acids may accumulate in zone 1. This willbe indicated by a pH (or acidity) probe 800, and respective signals willbe sent to the controller 830. At a preselected set point X₁, controllersends signals to actuators 820 and/or 32. When acidity increases (or pHdrops), the rate of the conditioned sludge supply from the selectedcompartment 4 to reaction zone 1 should be increased. This can beachieved by (1) opening of the motorized valve 820b and closing thevalve 820a, (2) increasing the pumping rate of a continuously run pump32, for example by controlling its speed, (3) by increasing theproportion of on/off times for a periodically run pump 32, or (4) acombination of these, or by alternative methods. When acidity deceases(pH rises) to a preselected point X₂, controller 830 sends signals toactuators 820 and 32 to reduce the feed rate of the conditioned sludgeto the reaction zone 1.

For each compartment 4, the controller 830 computes inventory of thesludge recycled to the reaction zone 1 from the moment of selecting(putting as recycle). The inventory can be computed for the givencompartment 4 volume known flowrate produced by pumps 32, and registeredtiming of operation of pumps 32 and valves 820a and 820b. After acomplete turnover of sludge in a selected compartment 4, or some longertime, but insuring the required quality of sludge being recycled, nextin que compartment 4 is selected. Periodically, inventory controls mustbe corrected manually.

Provisions that are standard for all control systems focused onperformance and stability are not described here, but the novelty,usefulness, and nonobviousness of the present controls is stressed: Theprocess control by recycling conditioned sludge is possible and veryeconomical due to the following: (1) the use of a partial phaseseparation between reaction zone 1 (growth of acidogens and supply ofmethanogens) and sludge conditioning compartments 3 in FIG. 1, or 4 inFIG. 2, or 5 in FIG. 3; and (2) the concentrating (thickening) of theconditioned sludge in the sludge conditioning compartments. Moreover, itis possible to conduct a partial (incomplete) treatment of wastewater bysetting X₁ value at a level corresponding to a relatively high residual(not consumed by methanogens) content of fatty acids. Such anarrangement is favorable for anaerobic-aerobic combinations, especiallywith nitrogen removal, wherein a carbon source should be passed to thedownstream process steps. Partial treatment without sludge conditionerand automatic controls; would be very unstable because of the highlyvariable growth rate of methanogens in the reactor. The inventory ofconditioned sludge allows for a stable operation of the incompletetreatment by delivering the required quantity of separately cultivatedconditioned sludge.

Stabilized incomplete treatment assumes permanent presence of fattyacids in the system. Accordingly sulfur reducers would propagate andhydrogen sulfide would be generated. To avoid the growth of sulfurreducers, the set point X₁ can be a variable in accordance with apreprogrammed algorithm in the controller 830: the value of X₁ shouldperiodically change from that corresponding to the complete treatment tothat corresponding to a lower level of the incomplete treatment than thedesign level. Concentrations of fatty acids will vary from almost zeroat the complete treatment periods to greater than the average designvalues. However, the average concentrations of fatty acids will be therequired concentrations. Using a variable X₁ set point, and periods ofalmost zero fatty acids content, the propagation of sulfur reducers willbe suppressed. Small quantities of sulfide generated in such operationwill react with the sulfates to form elementary sulfur and water. Thecurrent X₁ value can be set by using a simple step-wise timing, or anymore complex algorithm, for example, an algorithm computing the balanceof fatty acids, or a comprehensive pharmacodynamic model can be used.Insuring a process stability in case of the variable X₁ value ispossible only with the use of a pool of methanogens, reserve alkalinity,and other constituents deliverable on demand from the sludgeconditioner.

Referring now to FIG. 44, there are shown additional variants of thecontrol system. The control system is provided with a gas flow meter 801and gas analyzers 802 for methane (or total hydrocarbons), carbondioxide and, optionally, for hydrogen sulfide. An additional outputsignal line 813 from the control means 830 to the feed means (not shown)is also provided. A probe 821 for COD or TOC or both and a flow meter822 for the feed are optionally provided and connected to the controller830 by input signal lines 823 and 824. An optional output signal line813 connects controller 830 with means for controlling the feed flow inthe reaction zone 1.

The control system in FIG. 44 includes the procedures related to FIG.43. These will not be repeated. The gas flow is measured by the flowmeter 801, and the ratio CH₄ /CO₂ is determined by the probe 802. Whenthe ratio CH₄ /CO₂ decreases and the total gas flow increases, and pHdrops, the process in the reaction zone 1 shifts toward the acidogenicphase. The controller 830 increases the recycle rate of the conditionedsludge as previously described. A short term pH drop without noticeabledecreases in the CH₄ /CO₂ ratio is probably caused by a slug of mineralacid. This will be first neutralized by an increase in the conditionedsludge recycle rate. After a predetermined time, if pH is not broughtabove the set point of X₁, the system for feeding strong alkali (notshown) is actuated. The latter is conventional neutralization and is notdescribed here. At a pH above set point X₂, the control actions are thesame as previously described.

Optionally, COD or TOC probe 821 and the flow meter 822 are used tocompute the organic loading rate. The gas flow measured by the flowmeter 801 is correlated with the loading rate. When both changeproportionally, controller 830 makes a decision to change theconditioned sludge recycle rate based on probes 800 band 802, but not801.

Specific cases such as an increase in the organic loading rate anddecrease in the gas production rate most probably signify a toxic slugin the feed. This can be controlled on a short term basis by increasingthe conditioned sludge recycle rate. If the condition persists, othermeasures such as adding PAC, reducing feed rate, or others should beinitiated. This can be done by using the output signal line 813 toactuate the respective control means (not shown). This is alsoconventional technology, so no further discussion should be required.

Referring now to FIG. 45, there is shown a control system for asequencing batch reactor as depicted in FIGS. 18 and 19. Similarly tothe two previous embodiments, the control system includes a pH (oracidity) probe 800 with signal line 804 going to the control means 830,and gas flow meter 801 and gas analyzer 802 with lines 805 and 806.Units 801 and 802 are installed on a pipe 34 attached to a bell 803 forcollecting the off gas for measuring gas rate and composition. Lines 811and 812 connect the controller 830 to actuators 32 (pumps) and 411(motorized valves). This portion of the system is operated during thebatch cycle as previously described but with the objective to minimizethe batching time by providing an adequate supply of methanogens duringthe cycle.

The system shown in FIG. 45 is also equipped with level indicators forminimum 818 and maximum 817 levels, and respective input signal lines808 and 807. Output signal lines 813 and 814 are provided for actuatingthe feed means (not shown, may be a pump) and the discharge means (notshown, may be a motorized valve). When the gas rate at the end of thebatch process drops to a predetermined rate, the settling process isinitiated by stopping the sludge recycle pump 32. After a predeterminedtime, a signal from the controller 830 to the discharge means is sentvia line 814 and treated wastewater is discharged to the level of theprobe 818. At this moment, a signal from the probe 818 goes via line 808to controller 830, and signals from controller 830 go to the dischargemeans (via line 814) to stop discharging, and with a small delay vialine 813 to the charging means to start pumping the next batch.Simultaneously, the pump 32 is actuated. When the water level reachesthe probe 817, signal lines 807 and 813 and the controller 830 are usedto stop the charging means.

It is clear from the discussions of embodiments given in FIGS. 43, 44,45 that the distinct and principal new feature of the novel controlsystem is in sensing the phase shift (trend towards more acidogenic orexcessively methanogenic conditions) and correcting it by changing theconditioned sludge recycle rate. Various sensing devices or combinationof devices can be used for indicating and measuring the phase shift: pHmeters, titrometers, oxidation-reduction potential (ORP) electrodes, gasprobes for CO₂, CH₄, H₂, H₂ S, and other means. This fundamentalprinciple is used in the simplest complete treatment systems and in amore sophisticated incomplete treatment systems with variable regimes ofthe fatty acids released downstream.

Referring now to FIG. 45, there is shown an automatic control system forthe process embodiment depicted in FIG. 35, which is a combinedanaerobic-aerobic system. The anaerobic portion of this system isdepicted in FIGS. 15, 16, and elements Of the control system are shownin FIGS. 44 and 45. Discussions of the described elements will not berepeated. Additional elements of the control system include sensors 861(ORP, O₂, NO^(X)) for measuring phase shifts between the aerobicorganics transformation and nitrification, and a sensor 862 for thesludge concentration in the section 15. These sensors are connected bythe input signal lines 865 and 866 to the control means 830. Othersensors and elements used in known prior art systems (for example, airflow meters) may also be used, but are considered trivial and are notdescribed herein. Motorized valves 843 and 850 are provided on air linessupplying air to the airlift 470 and to the aerators 217. Motorizedvalves 841 and 842 are installed on lines lib and hla for conveying theclarified anaerobic effluent to sections 15 and 600. Motorized valves844, 845 and 846 are installed on the effluent feed branches 9, 609 and119 going to the anaerobic reactor 1, and sections 600 and 15. Thesevalves are connected to the control means 830 by the output lines 874,875 and 876. Motorized valves 820 and 843 are installed on the sludgerecycle lines and are connected via lines 812 and 873 to the controller830. Motorized valves 847 and 848 are provided on the mixed liquor lines610 and 631 leading from the airlift 470 to the anaerobic reactor 1 andthe section 600. These valves are connected to the control means 830 bythe output signal lines 877 and 878.

The control system shown in FIG. 46 is operated as follows. Theanaerobic section comprising the reactor 1, sludge conditionercompartments 4, and associated means is operated and controlled in theregime of incomplete treatment as has been previously described. Thatdescription will not be repeated. The anaerobically treated wastewaterfrom the sludge separator 2 is split into two portions, one directed byline 11a in the section 600, and the other is conveyed into section 15.Both portions of the flow carry fatty acids and other aerobicallydegradable constituents, and also a residual nonbiodegradable fraction.These flows also carry nitrogen compounds, predominately as ammonia andorganic nitrogen. In section 15, nitrogen is largely converted intonitrites and nitrates. Recycle of the mixed liquor from the section 15in the reactor 1 and the section 600 causes nitrites and nitrates to bereduced to nitrogen. Several reduction mechanisms are operative:Biological denitrification, and chemical reaction with ammonia, bothresulting in elemental nitrogen. During denitrification, especially insection 600, toxic and recalcitrant organics are oxidized. Reaction withammonia causes a greater removal of nitrogen. Nitrification anddenitrification require a carbon source. In this case the carbon sourceis the fatty acids and other products of incomplete treatment inreactor 1. Accordingly, the objective of the automatic control system isto provide balanced nitrification and denitrification--chemical nitrogenremoval. This control is provided by the three interacting loops:

(1) nitrification-denitrification/chemical reaction loop,

(2) incomplete anaerobic treatment loop, and

(3) fatty acid displacement and anaerobic sludge advance loop.

The nitrification-denitrification loop is operated-as follows. A probe861 measures NO_(X) concentration and sends a signal via line 865 to thecontroller 830. If the measured value exceeds Y₁, the recycle rate ofmixed liquor from the section 15 to the section 600 is increased by thecommand from the controller 830 by increasing airlift pumping rate viafeeding more air (greater opening of valve 849), or by greater openingof the valve 848, or by both.

Simultaneously a proportional increase in the supply of the fatty acidsand other organics is effected by recycling a greater flow of mixedliquor from the section 15 to the reactor 1 via a greater opening ofvalve 847. A greater flow of mixed liquor into reactor 1 displaceslarger amount of fatty acids (as needed for denitrification) and bringsa greater mass of ammonia (as needed for chemical nitrogen reduction).The response for this action is fast because this is a low inertiahydraulic process.

Simultaneously with the increase in the fatty acids displacement rate,the already described control of the incomplete anaerobic treatment isreset towards producing more fatty acids. This process has already beendiscussed. Such a reset will not cause excessive acidification of thereactor 1 content because of the bicarbonate buffering due to therecycled mixed liquor and denitrification of NO_(X) in this liquor. Whenthe set point for NO_(X) in the section 15 reaches Y₂ (low level), allcorrections are stepped down.

The system should also have conventional controls for aeration airsupply and the solids inventory. This is not described here.

It follows from the description provided here that the novel anaerobictreatment method affords stable operation and control of theinterrelated anaerobic-aerobic treatment system by the use of multiplebut interrelated control loops and subsystems. In view of the above andforegoing description and discussion, it will be understood that thepresent invention provides waste management and treatment systems thatare great improvements over the prior art systems. In the systems of thepresent invention, optionally, technical oxygen or oxygen-enriched aircan be used in aerobic conditioning steps. In addition to supportingaerobic processes, oxygen derived from any source will produce heatingof the sludge, and the heat can be beneficial in all conditioning steps:the biological growth and matter transformation, and chemical processeswill be faster; and, the reduced water viscosity will acceleratesolid/water separation.

Anaerobic process step can be used for removing heavy metals from thesludge. Under aerobic conditions, these metals solubilize due tooxidation of sulfides and can be removed by separating some water withmetals from the sludge. A step of sludge heating by external means canbe also provided.

The sludge conditioning step can be further enhanced by the use ofreagents, for example sulfur-bearing materials for immobilization ofheavy metals in the form of sulfides, and aluminum or iron salts forphosphorus and hydrogen sulfide control, and additional feed of organicwaste. Organic solid waste or concentrated liquids, with or withoutwater content, can also be fed into the conditioning steps for thepurposes of treating these materials and enhancing sludge conditioning.These materials will also provide a mass for retaining specificconstituents of wastewater, particularly slow and poorly degradable andtoxic organics, and heavy metals. Simultaneously, combustible gas andfertilizer (biological solids with high nutrients and soil conditioningorganics) can be produced. If oxygen is used in the sludge conditioningsteps, heat can also be produced and utilized.

The conditioning process steps fulfill three major functions. First, aconsortium of microorganisms and pools of (a) chemical compounds, (b)alkalinity reserve, (c) nutrients and micronutrients, and (d) enzymesgenerated by various types of microorganisms can be cultivated andformed in sludge conditioning steps. Second, the sludge can be cleanedfrom undesirable constituents, for example, heavy metals, and excessiveamount of nutrients. Third, the constituents of wastewater which cannotbe sufficiently treated and transformed in the reaction steps (slowlyand poorly degradable and toxic) but can be incorporated in the sludgein the reaction step, for example by adsorption, biosorption,flocculation and coagulation with anaerobic sludge, are treated andlargely transformed into the target final treatment products (gas,biological solids, water) in the sludge conditioning steps due toprolonged retention time and favorable conditions (temperature, mixing,chemical environment) in the sludge conditioning zone.

The functions of sludge conditioning are not separated from reactionsteps in the known technologies, and therefore cannot be performed in acontrollable way. The sludge components necessary for the anaerobictreatment cannot be formed in conventional systems, or can be onlypartially formed at longer retention times. The balance between thenecessary components is difficult to maintain because there are nospecifically assigned steps for cultivating and producing thesecomponents. Recycling of the intentionally and specifically conditionedsludge in the anaerobic reactor provides the components necessary forthe anaerobic treatment of wastewater. Moreover, sludge conditionerholds a large sludge mass sufficient for process control.

The single most important conditioning effect is provided by cultivatingmethanogenic organisms in the conditioning process step. The growth rateof methanogens is very low as compared to acidogenic organisms.Accordingly, the retention time must be very long to maintain bothacidogens and methanogens in the anaerobic reactor. This is especiallydifficult at low substrate concentration, because the growth andaccumulation of methanogens becomes extremely slow. In systems with thesludge conditioner, methanogens are grown at a high substrate and sludgeconcentration in a small volume conditioner. Concentrations in thesludge conditioner are controllable independently of the regimes in theanaerobic reactor. Enzymes generated by methanogens and capable ofconverting fatty acids are also produced in the conditioning processstep. When wastewater influent is fed in the anaerobic reactor, the fastgrowing acidogenic organisms rapidly propagate, establish themselves ata sufficiently high concentration and produce fatty acids. Theconditioned sludge fed into this reactor brings methanogenic organismsand enzymes previously generated by these organisms at highconcentrations (which can be controlled by the design and by anoperator). Fatty acids generated by acidogens are rapidly consumed bythe recycled conditioned sludge rich with methanogens. Due to the fattyacids consumption by methanogens, the sulfur reducing organisms can becontrollably deprived of the carbon source, so they will not grow, andhydrogen sulfide will be produced in very small concentrations.Partially, organics in the anaerobic reactor are adsorbed in thebiological flocks of sludge, suspended solids are flocculated andcoagulated by the biological sludge. The sludge loaded with theseorganics is separated from the reactor effluent and undergoes the nextround Of conditioning, when the organics are largely decomposed andmethanogens are cultivated. This sludge management strategy providesadvantageous conditions for treatment of low strength waste, fordegradation of suspended solids, for degradation of slowly and poorlydegradable organics, and toxic organics. It also insures the stablepresence of acidogenic and methanogenic organisms in the anaerobicreactor. The conditioned sludge contains substantial amounts ofbicarbonates which provide good pH buffering. This buffering, due to therecycled conditioned sludge and the uninterrupted presence ofmethanogens, precludes acidification of the reactor contents.

The propagation, accumulation, and retention of methanogens in thesludge conditioner facilitates rapid start up of anaerobic systems.Systems with sludge conditioners can be started in weeks, or a fewmonths.

Massive toxic shocks affect only the biomass present in the reactor atthe time of the slug. The bulk of the sludge inventory is storedoff-line in the sludge conditioner, and therefore is spared frompoisoning.

Reduction of sulfur bearing species, for example, sulfates or organicshaving sulfur, results in controllable formation of sulfides. Most heavymetals form poorly soluble sulfides; therefore, heavy metals can beprecipitated and incorporated into sludge as salts of sulfides. If thesulfur content in the original wastewater influent is deficient,sulfur-containing reagents can be added to the reactor, or to the sludgeconditioner. For example, the following reagents can be used: elementalsulfur, sulfuric acid, polysulfides, aluminum sulfate. These reagentswill not increase the total dissolved solids (TDS) of the effluent, orwill increase it only slightly. Other reagents, for example sodiumsulfide or sodium sulfate, can also be used. However, these salts willincrease the TDS more significantly. Sulfide can be generated in aseparate section so that clean gases are still produced in the system.

The use of aluminum sulfate is also beneficial for removal of phosphates(a nutrient) in the form of poorly soluble aluminum phosphate, and forcoagulation of suspended solids and biological solids in the reactor,which can be helpful for the separation step. Virtually all aluminumwill be incorporated in the sludge.

If the contents of the sludge conditioner are heated, methanogens willgrow faster. Recycle of thus conditioned sludge and associated enzymesinto the anaerobic reactor will support a rapid degradation of fattyacids generated by the action of the acidogens, the organisms growingrelatively fast even at submesophilic temperatures. Accordingly, thewastewater can be treated at low temperatures. As an option, the sludgeheating can be provided by aerobic treatment of a portion or all thesludge being conditioned. Use of oxygen or oxygen-enriched air ishelpful for reducing the heat loss by eliminating the heating of thenitrogen in the air. Combined aerobic-anaerobic sludge conditioning willalso accelerate the sludge conditioning process and may be helpful indegrading certain compounds when oxidation and reduction reactions areuseful. The aerobic treatment stage can either precede the anaerobicconditioning stage, or be parallel to the anaerobic stage with sludgebeing fed from the anaerobic stage to the aerobic stage and recycledafter-heating, back to the anaerobic stage. A portion of the heatgenerated in the aerobic stage can be transferred to the anaerobic stageby the e of heat exchangers. Excess heat may be utilized for purposesother than waste treatment.

Removal and degradation of slowly and poorly degradable and toxicconstituents can be further enhanced by adding adsorbents, particularlypowdered activated carbon (PAC), to the wastewater influent or to thereactor, or to the sludge conditioner. PAC also improves the performanceof the sludge separation step. Organics adsorbed on the PAC are retainedin the system for a very long time. Moreover, the mobility of adsorbedorganics between the water and the sludge phases is very limited.Accordingly, a high degree of transformation can be achieved even forslowly and poorly degradable and toxic organics. Such organics mayinclude surfactants, dyes, and solvents, including halogenated solvents.In many industrial wastewater treatment systems, such organics aredischarged periodically or occasionally. In order to keep the sludgeadapted to such organics, a microfeed of such organics may be providedcontinuously.

Usually an anaerobic treatment system is a part of a wastewatertreatment plant. Interconnections and interdependencies between unitprocesses and operations in the entire system should be considered whenimproving separate treatment processes. A novel method of improvinghydraulic stability of anaerobic reactors includes the steps of feedinga variable flow of wastewater influent and a constant or variable flowof recycled water (after a given treatment unit, or after one or severalsubsequent units) into a fluid flow control box and discharging aconstant flow from the flow control box. The discharge flow is equal toor greater than the maximum design flow of the wastewater influent. Atany time, the sum of the feed to the control box is equal to, or greaterthan, the maximum design flow of the wastewater influent. The excess ofthe recycle feed to the control box is discharged to the point fromwhich it was taken for recycle. If needed, other recycle flows, forexample, recycle of activated sludges, and feed of reagents can beconsidered to make up a constant flow rate. This method insures aconstant flow rate through the treatment units. Accordingly, operationsof suspended sludge blanket reactors or clarifiers, settling tanks,filters, and other processes sensitive to the flow variations and surgesare completely stabilized. In addition to hydraulic stability,recirculation of water produces equalization of concentrations ofadmixtures and sludge. Moreover, recirculation of water into ananaerobic reactor after, for example, an aerobic treatment withnitrification will reduce the nitrates and nitrites in the recycledportion of water. Aerobically treated water is usually rich inbicarbonates. The reduction of nitrates and nitrites and feeding ofbicarbonates will increase alkalinity in the anaerobic reactor andreduce pH variations. Equalizations of flows, concentrations ofadmixtures and concentrations of sludge will improve stability of thebiological consortia in the system.

Removal of slowly and poorly degradable and toxic organics, and alsoheavy metals, can be further improved by the use of a multiple stageanaerobic system with sludge conditioning steps.

Such a system will also be able to increase the efficiency of organicsremoval as determined by COD or BOD. Preferably, the sludge from thedownstream stages is used in the upstream stages. The same or differentconditioning methods can be used in different stages. The improvedremoval of specific constituents is due to counterflow of water andsludge. In the first stage, the sludge meets specific constituents andremoves the bulk of them. This sludge is gradually discharged from thesystem. In the second stage, the wastewater with a significantlydepleted amount of specific constituents is contacting a cleaner sludge(sludge grown in the second stage on wastewater with depleted specificconstituents). This sludge removes the bulk of the residual specificconstituents in the wastewater. Accordingly, removal of specificadmixtures is improved in multistage systems. Some process steps andtreatment units for sludge conditioning can be shared by various processstages.

In the present invention, the improved sludge management strategy isprovided by splitting the growth of acidogenic and methanogenicorganisms into two separate and distinct steps: acidogens are grown inan anaerobic reactor in which the influent material is subjected to thesimultaneous treatment step, while the methanogenic organisms are grownand accumulated in large mass off-line (not necessarily on the sludgerecycle line) in a long retention time and high sludge concentrationreactor (conditioner), and fed in the quantity instantly needed into thesaid reactor to effect the second phase conversion of the influentmaterial simultaneously and within the same space with the first processphase. This improvement results in the novel mainstream system havingtwo different and separately grown but interactively managed sludges.The principle can be broadly applied for systems involving variousgroups of organisms, e.g. as previously described, aerobic andmethanogenic anaerobic. It is believed that such systems and sludgemanagement strategies have never been described in patent or otherliterature, or otherwise disclosed.

It will therefore be understood by those skilled in the art that theparticular embodiments of the invention here presented are by way ofillustration only, and are meant to be in no way restrictive; therefore,numerous changes and modifications may be made, and the full use ofequivalents resorted to, without departing from the spirit or scope ofthe invention as outlined in the appended claims.

What is claimed is:
 1. A method of wastewater treatment in a pipenetwork for collecting and transporting wastewater comprising the stepof feeding conditioned sludge in the said pipe network, whereby the saidconditioned sludge comprises organisms selected from the groupconsisting of nitrifying organisms, aerobic organisms, facultativeorganisms, anaerobic organisms, methanogenic organisms, and combinationsthereof.
 2. A method of wastewater treatment as claimed in claim 1 andfurther providing a wastewater treatment plant, wherein the saidconditioned sludge is generated at said wastewater treatment plant.
 3. Amethod of wastewater treatment as claimed in claim 1 and furtherproviding a step of generating said conditioned sludge from saidwastewater at the said pipe network.
 4. A method of wastewater treatmentas claimed in claim 1 and further providing a step of generating saidconditioned sludge from solid or liquid materials outside the said pipenetwork.
 5. A method of wastewater treatment as claimed in claim 1,wherein combustible gas is produced.
 6. A method of wastewater treatmentas described in claim 5 wherein the said gas is handled in a stepselected from a group consisting of discharge of the said gas to theatmosphere, collection and incineration of the said gas, collection andutilization of the said gas, and combinations thereof.
 7. A method ofwastewater treatment as claimed in claim 1, wherein said step ofproviding the conditioned sludge is selected from the group consistingof transporting said conditioned sludge via pipe lines, trucking saidconditioned sludge, and combination thereof.
 8. A method of wastewatertreatment as claimed in claim 1 wherein the said conditioned sludgecomprises organisms selected from the group consisting of nitrifyingorganisms, aerobic organisms, facultative organisms, anoxic organisms,anaerobic organisms, methanogenic organisms, and combinations thereof.9. A method of wastewater treatment as claimed in claim 1 wherein thesaid organisms are selected from the group consisting of attached growthorganisms, suspended growth organisms, organisms attached to particulatematerials, organisms forming granular sludge, and combinations thereof.10. A method of wastewater treatment as claimed in claim 1 wherein thesaid wastewater includes constituents of pollutants and the saidtreatment is controlling the said constituents of pollutants in the saidwastewater in the said pipe network, whereby the said pollutants areselected from the group consisting of BOD, COD, recalcitrant organics,toxic organics, heavy metals, nutrients, and combinations thereof.
 11. Amethod of wastewater treatment as claimed in claim 1 wherein the saidtreatment is controlling odors in the said pipe network.
 12. A method ofwastewater treatment as claimed in claim 1 wherein the said treatment iscontrolling corrosion in the said pipe network.
 13. A method ofwastewater treatment as claimed in claim 1 wherein the said conditionedsludge is provided at a controllable feed rate.
 14. A method ofwastewater treatment as claimed in claim 13 wherein the saidcontrollable feed rate is selected from the group including manualcontrols, automatic controls, and combinations thereof.
 15. A method ofwastewater treatment as claimed in claim 14 wherein the said automaticcontrol comprises steps of measuring the wastewater characteristics withat least one sensing device, determining the control action with the useof a controller, and applying the said control action to correct thefeed rate of the said conditioned sludge with the use of at least oneactuator.
 16. A method of wastewater treatment as claimed in claim 1wherein the said conditioned sludge is provided from at least one sludgeconditioning unit, the capacity of the said sludge conditioning unit isbalanced with the need in the conditioned sludge in the said pipenetwork.
 17. A method of wastewater treatment as claimed in claim 16wherein the said sludge conditioning unit is selected from the groupconsisting of anaerobic section, aerobic section, and combinationsthereof.
 18. A method of wastewater treatment as claimed in claim 1wherein the said conditioned sludge is additionally provided withreagents selected from the group consisting of nutrients, sulfur bearingreagents, coagulants, neutralizing agents, adsorbents including powderedactivated carbon, oxyions including nitrite and nitrate, liquid or solidorganics of plant, animal, or fossil origin, vitamins, biostimulators,microquantities of specific pollutants, and combinations thereof.
 19. Amethod of wastewater treatment as claimed in claim 3 wherein the saidconditioned sludge is produced from the said wastewater intanks providedat the said pipe network.
 20. A method of wastewater treatment asclaimed in claim 1 wherein the said conditioned sludge is provided in aconcentrated form.